Lactate Oxidation in Paracoccus denitrificans

We report proteomic, metabolomic, and biochemical studies that establish that the metabolism of lactate by P. denitrificans is mediated by two non-NAD-dependent lactate dehydrogenases. One prefers D-lactate over L-lactate (D-iLDH) and the other prefers L-lactate (L-iLDH). We cloned and produced the D-iLDH and characterized it. The Km for D-lactate was 34 μM, and for L-lactate it was 3.7 mM. Pyruvate was not a substrate, rendering the reaction unidirectional with lactate being converted to pyruvate for entry into the TCA cycle. The intracellular lactate was ∼14 mM such that both isomers could be metabolized by the enzyme. The enzyme has 1 FAD per molecule and utilizes a quinone rather than NAD+ as an electron acceptor. D-iLDH provides a direct entry of lactate reducing equivalents into the cytochrome chain, potentially explaining the high respiratory capacity of P. denitrificans in the presence of lactate.PMID:38631502 | DOI:10.1016/j.abb.2024.109988
Source: Archives of Biochemistry and Biophysics - Category: Biochemistry Authors: Source Type: research