The lactate racemaseenzyme (Lar) (EC 5.1.2.1) interconverts the D- and L-enantiomers of lactic acid. It is classified under the isomerase, racemase, epimerase, and enzyme acting on hydroxyl acids and derivatives classes of enzymes.[1] It is found in certain halophilic archaea, such as Haloarcula marismortui, and in a few species of bacteria, such as several Lactobacillus species (which produce D- and L-lactate) including Lactobacillus sakei, Lactobacillus curvatus, and Lactobacillus plantarum, as well as in non-lactic acid bacteria such as Clostridium beijerinckii. [2] The gene encoding lactate racemase in L. plantarum was identified as larA and shown to be associated with a widespread maturation system involving larB, larC1, larC2, and larE.[3] The optimal pH for its activity is 5.8-6.2 in L. sakei.[4]
The molecular weight of lactate racemase differs in the various organisms in which it has been found, ranging from 25,000 to 82,400 g/mol.[5] The structure of the enzyme from L. plantarum was solved by Jian Hu and Robert P. Hausinger of Michigan State University and co-workers there and elsewhere.[6] The protein contains a previously unknown covalently-linked nickel-pincer nucleotide (NPN) cofactor (pyridinium 3-thioamide-5-thiocarboxylic acid mononucleotide), where the nickel atom is bound to C4 of the pyridinium ring and two sulfur atoms. This cofactor participates in a proton-coupled hydride-transfer mechanism.[7]
There have been a number of recent studies on NPN cofactor synthesis by the LarB, LarE, and LarC proteins. LarB is a carboxylase/hydrolase of nicotinamide adenine dinucleotide (NAD), providing pyridinium-3,5-dicarboxylic acid mononucleotide and adenosine monophosphate (AMP).[8] LarE is an ATP-dependent sulfur transferase that converts the two substrate carboxyl groups into thioacids by sacrificing the sulfur atoms of a cysteine residue in the protein.[9] Finally, LarC inserts nickel into the organic ligand by a CTP-dependent process to complete synthesis of the NPN cofactor.[10]
Enzyme activityedit
In many of the species containing lactate racemase, the physiological role of the enzyme is to convert substrate D-lactate into L-lactate. In other species, such as L. plantarum, the cellular role is to transform L-lactate into D-lactate for incorporation into the cell wall.[2]
The in vitro reaction catalyzed by the enzyme reaches equilibrium at the point where approximately equimolar concentrations of the D- and L-isomers exist.[4]
L. plantarum initially produces L-lactate, which induces the activity of lactate racemase. By contrast, D-lactate represses lactate racemase activity in this species. Therefore, Lar activity appears to be regulated by the ratio of L-lactate/D-lactate. L. plantarum LarA represents a new type of nickel-dependent enzyme, due to its novel nickel-pincer ligand ligand cofactor.[6]
Importanceedit
Two pathways appear to exist in L. plantarum for transforming pyruvate into D-lactate. One of them involves the NAD-dependent lactate dehydrogenase that directly produces D-lactate (LdhD), and the other is through the sequential activities of an L-specific lactate dehydrogenase followed by lactate racemase. If the LdhD enzyme is inactivated or inhibited, lactate racemase provides the bacterium with a rescue pathway for the production of D-lactate.[2] This pathway is significant because the production of D-lactate in L. plantarum is linked to the biosynthesis of the cell wall. Mutants lacking LdhD activity that also had the lar operon deleted only produced L-lactate, and peptidoglycan biosynthesis was not able to occur.
^ abcGoffin P; Deghorain M; Mainardi J-L; et al. (2005). "Lactate racemization as a rescue pathway for supplying D-lactate to the cell wall biosynthesis machinery in Lactobacillus plantarum". J. Bacteriol. 187 (19): 6750–61. doi:10.1128/JB.187.19.6750-6761.2005. PMC1251571. PMID 16166538.
^Desguin B, Goffin P, Viaene E, Kleerebezem M, Martin-Diaconescu V, Maroney MJ, Declercq JP, Soumillion P, Hols P (2014). "Lactate racemase is a nickel-dependent enzyme activated by a widespread maturation system". Nat. Commun. 5: 3615. doi:10.1038/ncomms4615. PMC4066177. PMID 24710389.
^ abHiyama T, Fukui S, Kitahara K (1968). "Purification and Properties of Lactate Racemase from Lactobacillus sake". J. Biochem. 64 (1): 99–107. doi:10.1093/oxfordjournals.jbchem.a128870. PMID 5707819.
^. Archived from the original on 2016-03-03. Retrieved 2007-06-03.
^ abDesguin B, Zhang T, Soumillion P, Hols P, Hu J, Hausinger RP (2015). "A tethered niacin-derived pincer complex with a nickel-carbon bond in lactate racemase". Science. 349 (6243): 66–69. doi:10.1126/science.aab2272. PMID 26138974. S2CID 206637903.
^Rankin JA, Mauban RC, Fellner M, Desguin B, McCracken J, Hu J, Varganov SA, Hausinger RP (2018). "Lactate Racemase Nickel-Pincer Cofactor Operates by a Proton-Coupled Hydride Transfer Mechanism". Biochemistry. 57 (23): 3244–3251. doi:10.1021/acs.biochem.8b00100. OSTI 1502215. PMID 29489337.
^Desguin B, Soumillion P, Hols P, Hausinger RP (2016). "Nickel-pincer cofactor biosynthesis involves LarB-catalyzed pyridinium carboxylation and LarE-dependent sacrificial sulfur insertion". Proc. Natl. Acad. Sci. USA. 113 (20): 5598–5603. doi:10.1073/pnas.1600486113. PMC4878509. PMID 27114550.
^Fellner M, Rankin JA, Desguin B, Hu J, Hausinger RP (2018). "Analysis of the Active Site Cysteine Residue of the Sacrificial Sulfur Insertase LarE from Lactobacillus plantarum". Biochemistry. 57 (38): 5513–5523. doi:10.1021/acs.biochem.8b00601. OSTI 1476089. PMID 30157639. S2CID 52117187.
^Desguin B, Fellner M, Riant O, Hu J, Hausinger RP, Hols P, Soumillion P (2018). "Biosynthesis of the nickel-pincer nucleotide cofactor of lactate racemase requires a CTP-dependent cyclometallase". J. Biol. Chem. 293 (32): 12303–12317. doi:10.1074/jbc.RA118.003741. PMC6093250. PMID 29887527.
lactate, racemase, lactate, racemase, enzyme, interconverts, enantiomers, lactic, acid, classified, under, isomerase, racemase, epimerase, enzyme, acting, hydroxyl, acids, derivatives, classes, enzymes, found, certain, halophilic, archaea, such, haloarcula, ma. The lactate racemase enzyme Lar EC 5 1 2 1 interconverts the D and L enantiomers of lactic acid It is classified under the isomerase racemase epimerase and enzyme acting on hydroxyl acids and derivatives classes of enzymes 1 It is found in certain halophilic archaea such as Haloarcula marismortui and in a few species of bacteria such as several Lactobacillus species which produce D and L lactate including Lactobacillus sakei Lactobacillus curvatus and Lactobacillus plantarum as well as in non lactic acid bacteria such as Clostridium beijerinckii 2 The gene encoding lactate racemase in L plantarum was identified as larA and shown to be associated with a widespread maturation system involving larB larC1 larC2 and larE 3 The optimal pH for its activity is 5 8 6 2 in L sakei 4 Lactate racemaseIdentifiersEC no 5 1 2 1CAS no 2602118DatabasesIntEnzIntEnz viewBRENDABRENDA entryExPASyNiceZyme viewKEGGKEGG entryMetaCycmetabolic pathwayPRIAMprofilePDB structuresRCSB PDB PDBe PDBsumSearchPMCarticlesPubMedarticlesNCBIproteins Contents 1 Structure and properties 2 Enzyme activity 3 Importance 4 ReferencesStructure and properties editThe molecular weight of lactate racemase differs in the various organisms in which it has been found ranging from 25 000 to 82 400 g mol 5 The structure of the enzyme from L plantarum was solved by Jian Hu and Robert P Hausinger of Michigan State University and co workers there and elsewhere 6 The protein contains a previously unknown covalently linked nickel pincer nucleotide NPN cofactor pyridinium 3 thioamide 5 thiocarboxylic acid mononucleotide where the nickel atom is bound to C4 of the pyridinium ring and two sulfur atoms This cofactor participates in a proton coupled hydride transfer mechanism 7 There have been a number of recent studies on NPN cofactor synthesis by the LarB LarE and LarC proteins LarB is a carboxylase hydrolase of nicotinamide adenine dinucleotide NAD providing pyridinium 3 5 dicarboxylic acid mononucleotide and adenosine monophosphate AMP 8 LarE is an ATP dependent sulfur transferase that converts the two substrate carboxyl groups into thioacids by sacrificing the sulfur atoms of a cysteine residue in the protein 9 Finally LarC inserts nickel into the organic ligand by a CTP dependent process to complete synthesis of the NPN cofactor 10 Enzyme activity editIn many of the species containing lactate racemase the physiological role of the enzyme is to convert substrate D lactate into L lactate In other species such as L plantarum the cellular role is to transform L lactate into D lactate for incorporation into the cell wall 2 The in vitro reaction catalyzed by the enzyme reaches equilibrium at the point where approximately equimolar concentrations of the D and L isomers exist 4 L plantarum initially produces L lactate which induces the activity of lactate racemase By contrast D lactate represses lactate racemase activity in this species Therefore Lar activity appears to be regulated by the ratio of L lactate D lactate L plantarum LarA represents a new type of nickel dependent enzyme due to its novel nickel pincer ligand ligand cofactor 6 Importance editTwo pathways appear to exist in L plantarum for transforming pyruvate into D lactate One of them involves the NAD dependent lactate dehydrogenase that directly produces D lactate LdhD and the other is through the sequential activities of an L specific lactate dehydrogenase followed by lactate racemase If the LdhD enzyme is inactivated or inhibited lactate racemase provides the bacterium with a rescue pathway for the production of D lactate 2 This pathway is significant because the production of D lactate in L plantarum is linked to the biosynthesis of the cell wall Mutants lacking LdhD activity that also had the lar operon deleted only produced L lactate and peptidoglycan biosynthesis was not able to occur References edit DBGET Result ENZYME 5 1 2 1 Retrieved 2007 06 03 a b c Goffin P Deghorain M Mainardi J L et al 2005 Lactate racemization as a rescue pathway for supplying D lactate to the cell wall biosynthesis machinery in Lactobacillus plantarum J Bacteriol 187 19 6750 61 doi 10 1128 JB 187 19 6750 6761 2005 PMC 1251571 PMID 16166538 Desguin B Goffin P Viaene E Kleerebezem M Martin Diaconescu V Maroney MJ Declercq JP Soumillion P Hols P 2014 Lactate racemase is a nickel dependent enzyme activated by a widespread maturation system Nat Commun 5 3615 doi 10 1038 ncomms4615 PMC 4066177 PMID 24710389 a b Hiyama T Fukui S Kitahara K 1968 Purification and Properties of Lactate Racemase from Lactobacillus sake J Biochem 64 1 99 107 doi 10 1093 oxfordjournals jbchem a128870 PMID 5707819 BRENDA Entry of Lactate racemase EC Number 5 1 2 1 Archived from the original on 2016 03 03 Retrieved 2007 06 03 a b Desguin B Zhang T Soumillion P Hols P Hu J Hausinger RP 2015 A tethered niacin derived pincer complex with a nickel carbon bond in lactate racemase Science 349 6243 66 69 doi 10 1126 science aab2272 PMID 26138974 S2CID 206637903 Rankin JA Mauban RC Fellner M Desguin B McCracken J Hu J Varganov SA Hausinger RP 2018 Lactate Racemase Nickel Pincer Cofactor Operates by a Proton Coupled Hydride Transfer Mechanism Biochemistry 57 23 3244 3251 doi 10 1021 acs biochem 8b00100 OSTI 1502215 PMID 29489337 Desguin B Soumillion P Hols P Hausinger RP 2016 Nickel pincer cofactor biosynthesis involves LarB catalyzed pyridinium carboxylation and LarE dependent sacrificial sulfur insertion Proc Natl Acad Sci USA 113 20 5598 5603 doi 10 1073 pnas 1600486113 PMC 4878509 PMID 27114550 Fellner M Rankin JA Desguin B Hu J Hausinger RP 2018 Analysis of the Active Site Cysteine Residue of the Sacrificial Sulfur Insertase LarE from Lactobacillus plantarum Biochemistry 57 38 5513 5523 doi 10 1021 acs biochem 8b00601 OSTI 1476089 PMID 30157639 S2CID 52117187 Desguin B Fellner M Riant O Hu J Hausinger RP Hols P Soumillion P 2018 Biosynthesis of the nickel pincer nucleotide cofactor of lactate racemase requires a CTP dependent cyclometallase J Biol Chem 293 32 12303 12317 doi 10 1074 jbc RA118 003741 PMC 6093250 PMID 29887527 Portal nbsp Biology Retrieved from https en wikipedia org w index php title Lactate racemase amp oldid 1172351723, wikipedia, wiki, book, books, library,
