Publications

• The catalytic action of human d-lactate dehydrogenase is severely inhibited by oxalate and is impaired by mutations triggering d-lactate acidosis.

  Stefan A., Mucchi A., Hochkoeppler A.

  d-lactate dehydrogenases are known to be expressed by prokaryotes and by eukaryotic invertebrates, and over the years the functional and structural features of some bacterial representatives of this enzyme ensemble have been investigated quite in detail. Remarkably, a human gene coding for a putat ... >> More

  d-lactate dehydrogenases are known to be expressed by prokaryotes and by eukaryotic invertebrates, and over the years the functional and structural features of some bacterial representatives of this enzyme ensemble have been investigated quite in detail. Remarkably, a human gene coding for a putative d-lactate dehydrogenase (DLDH) was identified and characterized, disclosing the occurrence of alternative splicing of its primary transcript. This translates into the expression of two human DLDH (hDLDH) isoforms, the molecular mass of which is expected to differ by 2.7 kDa. However, no information on these two hDLDH isoforms is available at the protein level. Here we report on the catalytic action of these enzymes, along with a first analysis of their structural features. In particular, we show that hDLDH is strictly stereospecific, with the larger isoform (hDLDH-1) featuring higher activity at the expense of d-lactate when compared to its smaller counterpart (hDLDH-2). Furthermore, we found that hDLDH is strongly inhibited by oxalate, as indicated by a K_i equal to 1.2 μM for this dicarboxylic acid. Structurally speaking, hDLDH-1 and hDLDH-2 were determined, by means of gel filtration and dynamic light scattering experiments, to be a hexamer and a tetramer, respectively. Moreover, in agreement with previous studies performed with human mitochondria, we identified FAD as the cofactor of hDLDH, and we report here a model of FAD binding by the human d-lactate dehydrogenase. Interestingly, the mutations W323C and T412 M negatively affect the activity of hDLDH, most likely by impairing the enzyme electron-acceptor site. << Less

  Arch Biochem Biophys 754:109932-109932(2024) [PubMed] [EuropePMC]

• Lactate dehydrogenase D is a general dehydrogenase for D-2-hydroxyacids and is associated with D-lactic acidosis.

  Jin S., Chen X., Yang J., Ding J.

  Mammalian lactate dehydrogenase D (LDHD) catalyzes the oxidation of D-lactate to pyruvate. LDHD mutations identified in patients with D-lactic acidosis lead to deficient LDHD activity. Here, we perform a systematic biochemical study of mouse LDHD (mLDHD) and determine the crystal structures of mLD ... >> More

  Mammalian lactate dehydrogenase D (LDHD) catalyzes the oxidation of D-lactate to pyruvate. LDHD mutations identified in patients with D-lactic acidosis lead to deficient LDHD activity. Here, we perform a systematic biochemical study of mouse LDHD (mLDHD) and determine the crystal structures of mLDHD in FAD-bound form and in complexes with FAD, Mn²⁺ and a series of substrates or products. We demonstrate that mLDHD is an Mn²⁺-dependent general dehydrogenase which exhibits catalytic activity for D-lactate and other D-2-hydroxyacids containing hydrophobic moieties, but no activity for their L-isomers or D-2-hydroxyacids containing hydrophilic moieties. The substrate-binding site contains a positively charged pocket to bind the common glycolate moiety and a hydrophobic pocket with some elasticity to bind the varied hydrophobic moieties of substrates. The structural and biochemical data together reveal the molecular basis for the substrate specificity and catalytic mechanism of LDHD, and the functional roles of mutations in the pathogenesis of D-lactic acidosis. << Less

  Nat Commun 14:6638-6638(2023) [PubMed] [EuropePMC]

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