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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1j49

E.C. nameD-lactate dehydrogenase
SpeciesLactobacillus delbrueckii subsp. bulgaricus (strain ATCC BAA-365)
E.C. Number (IntEnz) 1.1.1.28
CSA Homologues of 1j491dld,1dxy,1j4a,2dld,
CSA Entries With UniProtID P26297
CSA Entries With EC Number 1.1.1.28
PDBe Entry 1j49
PDBSum Entry 1j49
MACiE Entry 1j49

Literature Report

IntroductionD -Lactate dehydrogenase from Lactobacillus bulgaricus, a homodimer with 332 amino acid, acts at the last step of the glycolytic pathway under anaerobic conditions, allowing re-oxidation of NAD, which is necessary for glycolysis. The enzyme catalyses the NAD-dependent conversion of pyruvate into the D -isomer of lactic acid. The reaction is reversible: pyruvate reduction (the forward reaction) shows a maximum rate at pH 7.5 and D-lactate oxidation (the inverse reaction) at pH 8.0. The reaction leading to the other enantiomer, L-lactic acid, is catalysed by another enzyme, L-lactate dehydrogenase (L-LDH). While L-LDH has a wide occurrence in nature, D-LDH is found only in invertebrates, lower fungi and prokaryotic organisms. Lactic bacteria possess either one or both enzymes. In L.bulgaricus, commonly used in the dairy industry for the production of yoghurt, more than 90% of the pyruvate is converted into D-lactate.
MechansimWith reference to the known mechanism of L-lactate dehydrogenases, the reaction proceeds first with a proton being donated from (R)-lactate by His297 then a simultaneous proton donation to His267 and a hydride being transferred to NAD+, with help by Arg236 and Asp260 residues.
Reaction

Catalytic Sites for 1j49

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
HisA297297macie:sideChainActs as a general acid/base and abstracts and donates a proton from pyruvate to form D-lactate.
ArgA236236macie:sideChainPolarises the carbonyl bond in the pyruvate molecule to activate the hydride transfer.
AspA260260macie:sideChainAsp260 twists the NAD+ carboxamide by 21 degrees from the pyridine plane and fixing its oxygen in the cis-orientation with respect to C4N. This conformation has been shown to be unfavourable in isolated NADH/NAD+ molecules, because of the partial double-bond character of the C3N±C4N bond, but it is important in the activation of hydride transfer in dehydrogenases.
GluA265265macie:sideChainH-bonds to His297 to stabilise the protonated form, increasing its pKa and aid in its function as a base in the concerted step

Literature References

Notes:
Razeto A
Domain closure, substrate specificity and catalysis of D-lactate dehydrogenase from Lactobacillus bulgaricus.
J Mol Biol 2002 318 109-119
PubMed: 12054772
Kochhar S
Roles of his205, his296, his303 and Asp259 in catalysis by NAD+-specific D-lactate dehydrogenase.
Eur J Biochem 2000 267 1633-1639
PubMed: 10712593
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