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Lactase

February 15, 2024

Not to be confused with Lactose.

Lactase (EC 3.2.1.108) is an enzyme produced by many organisms and is essential to the complete digestion of whole milk. It breaks down the sugar lactose into its component parts, galactose and glucose. Lactase is found in the brush border of the small intestine of humans and other mammals. People deficient in lactase or lacking functional lactase may experience the symptoms of lactose intolerance after consuming milk products.[1] Lactase can be purchased as a food supplement and is added to milk to produce "lactose-free" milk products.

Lactase
E. coli lactase tetramer. PDB: 1JYN​
Identifiers
EC no.3.2.1.108
CAS no.9031-11-2
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO
Search
PMCarticles
PubMedarticles
NCBIproteins
Lactase
Identifiers
SymbolLCT
Alt. symbolsLAC; LPH; LPH1
NCBI gene3938
HGNC6530
OMIM603202
RefSeqNM_002299
UniProtP09848
Other data
EC number3.2.1.108
LocusChr. 2 q21
Search for
StructuresSwiss-model
DomainsInterPro

Uses edit

Food use edit

Lactase is an enzyme that some people are unable to produce in their small intestine.[2] Technology to produce lactose-free milk, ice cream, and yogurt was developed by the USDA Agricultural Research Service in 1985.[3] This technology is used to add lactase to milk, thereby hydrolyzing the lactose naturally found in milk, leaving it slightly sweet but digestible by everyone.[4] Without lactase, lactose intolerant people pass the lactose undigested to the colon[5] where bacteria break it down, creating carbon dioxide and that leads to bloating and flatulence.

Medical use edit

Lactase supplements can be used to treat lactose intolerance.[6]

Industrial use edit

Lactase produced commercially can be extracted both from yeasts such as Kluyveromyces fragilis and Kluyveromyces lactis and from molds, such as Aspergillus niger and Aspergillus oryzae.[7] Its primary commercial use in supplements is to break down lactose in milk to make it suitable for people with lactose intolerance.[8][9] The U.S. Food and Drug Administration has not independently evaluated these products.[10]

Lactase (or a similar form of β-galactosidase) is also used to screen for blue white colonies in the multiple cloning sites of various plasmid vectors in Escherichia coli or other bacteria.[11][12]

Mechanism edit

The optimum temperature for human lactase is about 37 °C[13] and the optimum pH is 6.[14]

In metabolism, the β-glycosidic bond in D-lactose is hydrolyzed to form D-galactose and D-glucose, which can be absorbed through the intestinal walls and into the bloodstream. The overall reaction that lactase catalyzes is as follows:

C12H22O11 + H2O → C6H12O6 + C6H12O6 + heat.
lactose + H2O → β-D-galactose + D-glucose

The catalytic mechanism of D-lactose hydrolysis retains the substrate anomeric configuration in the products.[15] While the details of the mechanism are uncertain, the stereochemical retention is achieved off a double displacement reaction. Studies of E. coli lactase have proposed that hydrolysis is initiated when a glutamate nucleophile on the enzyme attacks from the axial side of the galactosyl carbon in the β-glycosidic bond.[16] The removal of the D-glucose leaving group may be facilitated by Mg-dependent acid catalysis.[16] The enzyme is liberated from the α-galactosyl moiety upon equatorial nucleophilic attack by water, which produces D-galactose.[15]

Substrate modification studies have demonstrated that the 3′-OH and 2′-OH moieties on the galactopyranose ring are essential for enzymatic recognition and hydrolysis.[17] The 3′-hydroxy group is involved in initial binding to the substrate while the 2′- group is not necessary for recognition but needed in subsequent steps. This is demonstrated by the fact that a 2-deoxy analog is an effective competitive inhibitor (Ki = 10mM).[17] Elimination of specific hydroxyl groups on the glucopyranose moiety does not eliminate catalysis.[17]

 

Lactase also catalyzes the conversion of phlorizin to phloretin and glucose.

Lactase (Lactaid commercially )is used as a medication for lactose intolerance. Since it is a complex protein, it cannot be absorbed via the small intestine. However, it is packaged in an acid-proof tablet, allowing the protein to pass through the gastric acid, and remaining intact in the small intestine. Thus it can act in any lactose molecules digested, allowing the body to absorb them without leaving them indigested, which woold cause cramping and diarrhea. As the enzyme is not absorbed through the intestine, it is being excreeted in the next bowel movement.

Structure and biosynthesis edit

Preprolactase, the primary translation product, has a single polypeptide primary structure consisting of 1927 amino acids.[18] It can be divided into five domains: (i) a 19-amino-acid cleaved signal sequence; (ii) a large prosequence domain that is not present in mature lactase; (iii) the mature lactase segment; (iv) a membrane-spanning hydrophobic anchor; and (v) a short hydrophilic carboxyl terminus.[18] The signal sequence is cleaved in the endoplasmic reticulum, and the resulting 215-kDa pro-LPH is sent to the Golgi apparatus, where it is heavily glycosylated and proteolytically processed to its mature form.[19] The prodomain has been shown to act as an intramolecular chaperone in the ER, preventing trypsin cleavage and allowing LPH to adopt the necessary 3-D structure to be transported to the Golgi apparatus.[20]

 

Mature human lactase consists of a single 160-kDa polypeptide chain that localizes to the brush border membrane of intestinal epithelial cells. It is oriented with the N-terminus outside the cell and the C-terminus in the cytosol.[18] LPH contains two catalytic glutamic acid sites. In the human enzyme, the lactase activity has been connected to Glu-1749, while Glu-1273 is the site of phlorizin hydrolase function.[21]

Genetic expression and regulation edit

Lactase is encoded by a single genetic locus on chromosome 2.[22] It is expressed exclusively by mammalian small intestine enterocytes and in very low levels in the colon during fetal development.[22] Humans are born with high levels of lactase expression. In most of the world's population, lactase transcription is down-regulated after weaning, resulting in diminished lactase expression in the small intestine,[22] which causes the common symptoms of adult-type hypolactasia, or lactose intolerance.[23] The LCT gene provides the instructions for making lactase. Lactose intolerance in infants (congenital lactase deficiency) is caused by mutations in the LCT gene. Mutations are believed to interfere with the function of lactase, causing affected infants to have a severely impaired ability to digest lactose in breast milk or formula.[24]

Some population segments exhibit lactase persistence resulting from a mutation that is postulated to have occurred 5,000–10,000 years ago, coinciding with the rise of cattle domestication.[25] This mutation has allowed almost half of the world's population to metabolize lactose without symptoms. Studies have linked the occurrence of lactase persistence to two different single-nucleotide polymorphisms about 14 and 22 kilobases upstream of the 5’-end of the LPH gene.[26] Both mutations, C→T at position -13910 and G→ A at position -22018, have been independently linked to lactase persistence.[27]

The lactase promoter is 150 base pairs long and is located upstream of the site of transcription initiation.[27] The sequence is highly conserved in mammals, suggesting that critical cis-transcriptional regulators are located nearby.[27] Cdx-2, HNF-1α, and GATA have been identified as transcription factors.[27] Studies of hypolactasia onset have demonstrated that despite polymorphisms, little difference exists in lactase expression in infants, showing that the mutations become increasingly relevant during development.[28] Developmentally regulated DNA-binding proteins may down-regulate transcription or destabilize mRNA transcripts, causing decreased LPH expression after weaning.[28]

See also edit

References edit

  1. ^ Järvelä I, Torniainen S, Kolho KL (2009). "Molecular genetics of human lactase deficiencies". Annals of Medicine. 41 (8): 568–75. doi:10.1080/07853890903121033. PMID 19639477. S2CID 205586720.
  2. ^ "Lactose Intolerance". Mayo Clinic. Retrieved 13 March 2018.
  3. ^ Porch K (2018-04-12). "Lactose-Free Milk, Low-Fat Cheese, and More Dairy Breakthroughs". www.federallabs.org. Retrieved 2018-10-26.
  4. ^ "Asked: How do dairies make lactose-free milk?". USA Today. 3 September 2014. Retrieved 13 March 2018.
  5. ^ "Lactose intolerance - Symptoms and causes". Mayo Clinic. Retrieved 2020-11-08.
  6. ^ "Lactose Intolerance". NIDDK. June 2014. Retrieved 25 October 2016.
  7. ^ Seyis I, Aksoz N (2004). "Production of Lactase by Trichoderma sp". Food Technology and Biotechnology. 42 (2): 121–124.
  8. ^ DSM Food Specialties (3 April 2014). "GRAS Notification for Acid Lactase from Aspergillus oryzae Expressed in Aspergillus niger" (PDF). p. 1. Archived from the original on 31 October 2017 – via U.S. Food and Drug Administration.
  9. ^ Holsinger VH (1992). "Innovative Products for Food Industries: The Lactaid Story". New Crops, New Uses, New Markets: 1992 Yearbook of Agriculture. U.S. Department of Agriculture. pp. 256–258.
  10. ^ Tarantino, LM (12 December 2003). . U.S. Food and Drug Administration. Archived from the original on 26 March 2011.
  11. ^ Lau HM, Lee LS, Soh WC, Tue SW (March 2013). "Introduction". Lactase. Universiti Teknologi Malaysia. Retrieved 16 November 2018.
  12. ^ . Fermentas. Archived from the original on 19 October 2008.
  13. ^ Hermida C, Corrales G, Cañada FJ, Aragón JJ, Fernández-Mayoralas A (Jul 2007). "Optimizing the enzymatic synthesis of β-D-galactopyranosyl-D-xyloses for their use in the evaluation of lactase activity in vivo". Bioorganic & Medicinal Chemistry. 15 (14): 4836–40. doi:10.1016/j.bmc.2007.04.067. hdl:10261/81580. PMID 17512743.
  14. ^ Skovbjerg H, Sjöström H, Norén O (Mar 1981). "Purification and characterisation of amphiphilic lactase/phlorizin hydrolase from human small intestine". European Journal of Biochemistry. 114 (3): 653–61. doi:10.1111/j.1432-1033.1981.tb05193.x. PMID 6786877.
  15. ^ a b Sinnott M (November 1990). "Catalytic mechanisms of enzymic glycosyl transfer". Chem. Rev. 90 (7): 1171–1202. doi:10.1021/cr00105a006.
  16. ^ a b Juers DH, Heightman TD, Vasella A, McCarter JD, Mackenzie L, Withers SG, Matthews BW (Dec 2001). "A structural view of the action of Escherichia coli (lacZ) β-galactosidase". Biochemistry. 40 (49): 14781–94. doi:10.1021/bi011727i. PMID 11732897.
  17. ^ a b c Fernandez P, Cañada FJ, Jiménez-Barbero J, Martín-Lomas M (Jul 1995). "Substrate specificity of small-intestinal lactase: study of the steric effects and hydrogen bonds involved in enzyme-substrate interaction". Carbohydrate Research. 271 (1): 31–42. doi:10.1016/0008-6215(95)00034-Q. PMID 7648581.
  18. ^ a b c Mantei N, Villa M, Enzler T, Wacker H, Boll W, James P, Hunziker W, Semenza G (Sep 1988). "Complete primary structure of human and rabbit lactase-phlorizin hydrolase: implications for biosynthesis, membrane anchoring and evolution of the enzyme". The EMBO Journal. 7 (9): 2705–13. doi:10.1002/j.1460-2075.1988.tb03124.x. PMC 457059. PMID 2460343.
  19. ^ Naim HY, Sterchi EE, Lentze MJ (Jan 1987). "Biosynthesis and maturation of lactase-phlorizin hydrolase in the human small intestinal epithelial cells". The Biochemical Journal. 241 (2): 427–34. doi:10.1042/bj2410427. PMC 1147578. PMID 3109375.
  20. ^ Naim HY, Jacob R, Naim H, Sambrook JF, Gething MJ (Oct 1994). "The pro region of human intestinal lactase-phlorizin hydrolase". The Journal of Biological Chemistry. 269 (43): 26933–43. doi:10.1016/S0021-9258(18)47109-8. PMID 7523415.
  21. ^ Zecca L, Mesonero JE, Stutz A, Poirée JC, Giudicelli J, Cursio R, Gloor SM, Semenza G (Sep 1998). "Intestinal lactase-phlorizin hydrolase (LPH): the two catalytic sites; the role of the pancreas in pro-LPH maturation". FEBS Letters. 435 (2–3): 225–8. doi:10.1016/S0014-5793(98)01076-X. PMID 9762914. S2CID 33421778.
  22. ^ a b c Troelsen JT, Mitchelmore C, Spodsberg N, Jensen AM, Norén O, Sjöström H (Mar 1997). "Regulation of lactase-phlorizin hydrolase gene expression by the caudal-related homoeodomain protein Cdx-2". The Biochemical Journal. 322 ( Pt 3) (Pt. 3): 833–8. doi:10.1042/bj3220833. PMC 1218263. PMID 9148757.
  23. ^ Reference GH. "LCT gene". Genetics Home Reference. Retrieved 3 April 2018.
  24. ^ "Lactose intolerance: MedlinePlus Genetics". medlineplus.gov. Retrieved 2022-03-22.
  25. ^ Bersaglieri T, Sabeti PC, Patterson N, Vanderploeg T, Schaffner SF, Drake JA, Rhodes M, Reich DE, Hirschhorn JN (Jun 2004). "Genetic signatures of strong recent positive selection at the lactase gene". American Journal of Human Genetics. 74 (6): 1111–20. doi:10.1086/421051. PMC 1182075. PMID 15114531.
  26. ^ Kuokkanen M, Enattah NS, Oksanen A, Savilahti E, Orpana A, Järvelä I (May 2003). "Transcriptional regulation of the lactase-phlorizin hydrolase gene by polymorphisms associated with adult-type hypolactasia". Gut. 52 (5): 647–52. doi:10.1136/gut.52.5.647. PMC 1773659. PMID 12692047.
  27. ^ a b c d Troelsen JT (May 2005). "Adult-type hypolactasia and regulation of lactase expression". Biochimica et Biophysica Acta (BBA) - General Subjects. 1723 (1–3): 19–32. doi:10.1016/j.bbagen.2005.02.003. PMID 15777735.
  28. ^ a b Wang Y, Harvey CB, Hollox EJ, Phillips AD, Poulter M, Clay P, Walker-Smith JA, Swallow DM (Jun 1998). "The genetically programmed down-regulation of lactase in children". Gastroenterology. 114 (6): 1230–6. doi:10.1016/S0016-5085(98)70429-9. PMID 9609760.

External links edit

 
Wikimedia Commons has media related to Lactase.
  • The Lactase Protein
  • E. coli β-galactosidase: PDB: 1JYY​
  • Gene Ontology for Lactase
  • Making of the Fittest: Got Lactase? The Co-evolution of Genes and Culture
  • Lactase persistence shows indication of association with Obesity
  • PDBe-KB provides an overview of all the structure information available in the PDB for Human Beta-galactosidase
  • PDBe-KB provides an overview of all the structure information available in the PDB for Escherichia coli Beta-galactosidase

February 15, 2024
lactase, confused, with, lactose, enzyme, produced, many, organisms, essential, complete, digestion, whole, milk, breaks, down, sugar, lactose, into, component, parts, galactose, glucose, found, brush, border, small, intestine, humans, other, mammals, people, . Not to be confused with Lactose Lactase EC 3 2 1 108 is an enzyme produced by many organisms and is essential to the complete digestion of whole milk It breaks down the sugar lactose into its component parts galactose and glucose Lactase is found in the brush border of the small intestine of humans and other mammals People deficient in lactase or lacking functional lactase may experience the symptoms of lactose intolerance after consuming milk products 1 Lactase can be purchased as a food supplement and is added to milk to produce lactose free milk products LactaseE coli lactase tetramer PDB 1JYN IdentifiersEC no 3 2 1 108CAS no 9031 11 2DatabasesIntEnzIntEnz viewBRENDABRENDA entryExPASyNiceZyme viewKEGGKEGG entryMetaCycmetabolic pathwayPRIAMprofilePDB structuresRCSB PDB PDBe PDBsumGene OntologyAmiGO QuickGOSearchPMCarticlesPubMedarticlesNCBIproteinsLactaseIdentifiersSymbolLCTAlt symbolsLAC LPH LPH1NCBI gene3938HGNC6530OMIM603202RefSeqNM 002299UniProtP09848Other dataEC number3 2 1 108LocusChr 2 q21Search forStructuresSwiss modelDomainsInterPro Contents 1 Uses 1 1 Food use 1 2 Medical use 1 3 Industrial use 2 Mechanism 3 Structure and biosynthesis 4 Genetic expression and regulation 5 See also 6 References 7 External linksUses editFood use edit Lactase is an enzyme that some people are unable to produce in their small intestine 2 Technology to produce lactose free milk ice cream and yogurt was developed by the USDA Agricultural Research Service in 1985 3 This technology is used to add lactase to milk thereby hydrolyzing the lactose naturally found in milk leaving it slightly sweet but digestible by everyone 4 Without lactase lactose intolerant people pass the lactose undigested to the colon 5 where bacteria break it down creating carbon dioxide and that leads to bloating and flatulence Medical use edit Lactase supplements can be used to treat lactose intolerance 6 Industrial use edit Lactase produced commercially can be extracted both from yeasts such as Kluyveromyces fragilis and Kluyveromyces lactis and from molds such as Aspergillus niger and Aspergillus oryzae 7 Its primary commercial use in supplements is to break down lactose in milk to make it suitable for people with lactose intolerance 8 9 The U S Food and Drug Administration has not independently evaluated these products 10 Lactase or a similar form of b galactosidase is also used to screen for blue white colonies in the multiple cloning sites of various plasmid vectors in Escherichia coli or other bacteria 11 12 Mechanism editThe optimum temperature for human lactase is about 37 C 13 and the optimum pH is 6 14 In metabolism the b glycosidic bond in D lactose is hydrolyzed to form D galactose and D glucose which can be absorbed through the intestinal walls and into the bloodstream The overall reaction that lactase catalyzes is as follows C12H22O11 H2O C6H12O6 C6H12O6 heat lactose H2O b D galactose D glucoseThe catalytic mechanism of D lactose hydrolysis retains the substrate anomeric configuration in the products 15 While the details of the mechanism are uncertain the stereochemical retention is achieved off a double displacement reaction Studies of E coli lactase have proposed that hydrolysis is initiated when a glutamate nucleophile on the enzyme attacks from the axial side of the galactosyl carbon in the b glycosidic bond 16 The removal of the D glucose leaving group may be facilitated by Mg dependent acid catalysis 16 The enzyme is liberated from the a galactosyl moiety upon equatorial nucleophilic attack by water which produces D galactose 15 Substrate modification studies have demonstrated that the 3 OH and 2 OH moieties on the galactopyranose ring are essential for enzymatic recognition and hydrolysis 17 The 3 hydroxy group is involved in initial binding to the substrate while the 2 group is not necessary for recognition but needed in subsequent steps This is demonstrated by the fact that a 2 deoxy analog is an effective competitive inhibitor Ki 10mM 17 Elimination of specific hydroxyl groups on the glucopyranose moiety does not eliminate catalysis 17 nbsp Lactase also catalyzes the conversion of phlorizin to phloretin and glucose Lactase Lactaid commercially is used as a medication for lactose intolerance Since it is a complex protein it cannot be absorbed via the small intestine However it is packaged in an acid proof tablet allowing the protein to pass through the gastric acid and remaining intact in the small intestine Thus it can act in any lactose molecules digested allowing the body to absorb them without leaving them indigested which woold cause cramping and diarrhea As the enzyme is not absorbed through the intestine it is being excreeted in the next bowel movement Structure and biosynthesis editPreprolactase the primary translation product has a single polypeptide primary structure consisting of 1927 amino acids 18 It can be divided into five domains i a 19 amino acid cleaved signal sequence ii a large prosequence domain that is not present in mature lactase iii the mature lactase segment iv a membrane spanning hydrophobic anchor and v a short hydrophilic carboxyl terminus 18 The signal sequence is cleaved in the endoplasmic reticulum and the resulting 215 kDa pro LPH is sent to the Golgi apparatus where it is heavily glycosylated and proteolytically processed to its mature form 19 The prodomain has been shown to act as an intramolecular chaperone in the ER preventing trypsin cleavage and allowing LPH to adopt the necessary 3 D structure to be transported to the Golgi apparatus 20 nbsp Mature human lactase consists of a single 160 kDa polypeptide chain that localizes to the brush border membrane of intestinal epithelial cells It is oriented with the N terminus outside the cell and the C terminus in the cytosol 18 LPH contains two catalytic glutamic acid sites In the human enzyme the lactase activity has been connected to Glu 1749 while Glu 1273 is the site of phlorizin hydrolase function 21 Genetic expression and regulation editLactase is encoded by a single genetic locus on chromosome 2 22 It is expressed exclusively by mammalian small intestine enterocytes and in very low levels in the colon during fetal development 22 Humans are born with high levels of lactase expression In most of the world s population lactase transcription is down regulated after weaning resulting in diminished lactase expression in the small intestine 22 which causes the common symptoms of adult type hypolactasia or lactose intolerance 23 The LCT gene provides the instructions for making lactase Lactose intolerance in infants congenital lactase deficiency is caused by mutations in the LCT gene Mutations are believed to interfere with the function of lactase causing affected infants to have a severely impaired ability to digest lactose in breast milk or formula 24 Some population segments exhibit lactase persistence resulting from a mutation that is postulated to have occurred 5 000 10 000 years ago coinciding with the rise of cattle domestication 25 This mutation has allowed almost half of the world s population to metabolize lactose without symptoms Studies have linked the occurrence of lactase persistence to two different single nucleotide polymorphisms about 14 and 22 kilobases upstream of the 5 end of the LPH gene 26 Both mutations C T at position 13910 and G A at position 22018 have been independently linked to lactase persistence 27 The lactase promoter is 150 base pairs long and is located upstream of the site of transcription initiation 27 The sequence is highly conserved in mammals suggesting that critical cis transcriptional regulators are located nearby 27 Cdx 2 HNF 1a and GATA have been identified as transcription factors 27 Studies of hypolactasia onset have demonstrated that despite polymorphisms little difference exists in lactase expression in infants showing that the mutations become increasingly relevant during development 28 Developmentally regulated DNA binding proteins may down regulate transcription or destabilize mRNA transcripts causing decreased LPH expression after weaning 28 See also edit nbsp Biology portalMCM6 Lactase persistenceReferences edit Jarvela I Torniainen S Kolho KL 2009 Molecular genetics of human lactase deficiencies Annals of Medicine 41 8 568 75 doi 10 1080 07853890903121033 PMID 19639477 S2CID 205586720 Lactose Intolerance Mayo Clinic Retrieved 13 March 2018 Porch K 2018 04 12 Lactose Free Milk Low Fat Cheese and More Dairy Breakthroughs www federallabs org Retrieved 2018 10 26 Asked How do dairies make lactose free milk USA Today 3 September 2014 Retrieved 13 March 2018 Lactose intolerance Symptoms and causes Mayo Clinic Retrieved 2020 11 08 Lactose Intolerance NIDDK June 2014 Retrieved 25 October 2016 Seyis I Aksoz N 2004 Production of Lactase by Trichoderma sp Food Technology and Biotechnology 42 2 121 124 DSM Food Specialties 3 April 2014 GRAS Notification for Acid Lactase from Aspergillus oryzae Expressed in Aspergillus niger PDF p 1 Archived from the original on 31 October 2017 via U S Food and Drug Administration Holsinger VH 1992 Innovative Products for Food Industries The Lactaid Story New Crops New Uses New Markets 1992 Yearbook of Agriculture U S Department of Agriculture pp 256 258 Tarantino LM 12 December 2003 Agency Response Letter GRAS Notice No GRN 000132 U S Food and Drug Administration Archived from the original on 26 March 2011 Lau HM Lee LS Soh WC Tue SW March 2013 Introduction Lactase Universiti Teknologi Malaysia Retrieved 16 November 2018 pBluescript II KS pBluescript II SK description amp restriction map Fermentas Archived from the original on 19 October 2008 Hermida C Corrales G Canada FJ Aragon JJ Fernandez Mayoralas A Jul 2007 Optimizing the enzymatic synthesis of b D galactopyranosyl D xyloses for their use in the evaluation of lactase activity in vivo Bioorganic amp Medicinal Chemistry 15 14 4836 40 doi 10 1016 j bmc 2007 04 067 hdl 10261 81580 PMID 17512743 Skovbjerg H Sjostrom H Noren O Mar 1981 Purification and characterisation of amphiphilic lactase phlorizin hydrolase from human small intestine European Journal of Biochemistry 114 3 653 61 doi 10 1111 j 1432 1033 1981 tb05193 x PMID 6786877 a b Sinnott M November 1990 Catalytic mechanisms of enzymic glycosyl transfer Chem Rev 90 7 1171 1202 doi 10 1021 cr00105a006 a b Juers DH Heightman TD Vasella A McCarter JD Mackenzie L Withers SG Matthews BW Dec 2001 A structural view of the action of Escherichia coli lacZ b galactosidase Biochemistry 40 49 14781 94 doi 10 1021 bi011727i PMID 11732897 a b c Fernandez P Canada FJ Jimenez Barbero J Martin Lomas M Jul 1995 Substrate specificity of small intestinal lactase study of the steric effects and hydrogen bonds involved in enzyme substrate interaction Carbohydrate Research 271 1 31 42 doi 10 1016 0008 6215 95 00034 Q PMID 7648581 a b c Mantei N Villa M Enzler T Wacker H Boll W James P Hunziker W Semenza G Sep 1988 Complete primary structure of human and rabbit lactase phlorizin hydrolase implications for biosynthesis membrane anchoring and evolution of the enzyme The EMBO Journal 7 9 2705 13 doi 10 1002 j 1460 2075 1988 tb03124 x PMC 457059 PMID 2460343 Naim HY Sterchi EE Lentze MJ Jan 1987 Biosynthesis and maturation of lactase phlorizin hydrolase in the human small intestinal epithelial cells The Biochemical Journal 241 2 427 34 doi 10 1042 bj2410427 PMC 1147578 PMID 3109375 Naim HY Jacob R Naim H Sambrook JF Gething MJ Oct 1994 The pro region of human intestinal lactase phlorizin hydrolase The Journal of Biological Chemistry 269 43 26933 43 doi 10 1016 S0021 9258 18 47109 8 PMID 7523415 Zecca L Mesonero JE Stutz A Poiree JC Giudicelli J Cursio R Gloor SM Semenza G Sep 1998 Intestinal lactase phlorizin hydrolase LPH the two catalytic sites the role of the pancreas in pro LPH maturation FEBS Letters 435 2 3 225 8 doi 10 1016 S0014 5793 98 01076 X PMID 9762914 S2CID 33421778 a b c Troelsen JT Mitchelmore C Spodsberg N Jensen AM Noren O Sjostrom H Mar 1997 Regulation of lactase phlorizin hydrolase gene expression by the caudal related homoeodomain protein Cdx 2 The Biochemical Journal 322 Pt 3 Pt 3 833 8 doi 10 1042 bj3220833 PMC 1218263 PMID 9148757 Reference GH LCT gene Genetics Home Reference Retrieved 3 April 2018 Lactose intolerance MedlinePlus Genetics medlineplus gov Retrieved 2022 03 22 Bersaglieri T Sabeti PC Patterson N Vanderploeg T Schaffner SF Drake JA Rhodes M Reich DE Hirschhorn JN Jun 2004 Genetic signatures of strong recent positive selection at the lactase gene American Journal of Human Genetics 74 6 1111 20 doi 10 1086 421051 PMC 1182075 PMID 15114531 Kuokkanen M Enattah NS Oksanen A Savilahti E Orpana A Jarvela I May 2003 Transcriptional regulation of the lactase phlorizin hydrolase gene by polymorphisms associated with adult type hypolactasia Gut 52 5 647 52 doi 10 1136 gut 52 5 647 PMC 1773659 PMID 12692047 a b c d Troelsen JT May 2005 Adult type hypolactasia and regulation of lactase expression Biochimica et Biophysica Acta BBA General Subjects 1723 1 3 19 32 doi 10 1016 j bbagen 2005 02 003 PMID 15777735 a b Wang Y Harvey CB Hollox EJ Phillips AD Poulter M Clay P Walker Smith JA Swallow DM Jun 1998 The genetically programmed down regulation of lactase in children Gastroenterology 114 6 1230 6 doi 10 1016 S0016 5085 98 70429 9 PMID 9609760 External links edit nbsp Wikimedia Commons has media related to Lactase The Lactase Protein E coli b galactosidase PDB 1JYY Gene Ontology for Lactase Making of the Fittest Got Lactase The Co evolution of Genes and Culture Lactase persistence shows indication of association with Obesity PDBe KB provides an overview of all the structure information available in the PDB for Human Beta galactosidase PDBe KB provides an overview of all the structure information available in the PDB for Escherichia coli Beta galactosidase Retrieved from https en wikipedia org w index php title Lactase amp oldid 1203896449, wikipedia, wiki, book, books, 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