title: Membrane-bound, pyridine nucleotide-independent L-lactate dehydrogenase of Rhodopseudomonas sphaeroides.
abstract: Rhodopseudomonas sphaeroides has a pyridine nucleotide-independent L-lactate dehydrogenase associated with the membrane fraction of cells grown either aerobically or phototrophically. The dehydrogenase is present in cells grown on a variety of carbon sources, but at levels less than 20% of that found in cells grown with DL-lactate. The dehydrogenase has been purified 45-fold from membranes of strain L-57, a non-photosynthetic mutant, by steps involving solubilization with lauryl dimethylamine oxide and three anion-exchange chromatography steps. The purified enzyme was specific for the L-isomer of lactate. The Km of the purified enzyme for L-lactate is 1.4 mM, whereas that of the membrane-associated enzyme is 0.5 mM. The enzyme activity was inhibited competitively by D-lactate and non-competitively by oxalate and oxamate. Quinacrine, a flavin analog, also inhibited the activity. The inducible enzyme may serve as a marker of membrane protein in studies of membrane development.
mesh_terms: D002462:Cell Membrane / Q000201:enzymology; D002848:Chromatography, DEAE-Cellulose; D002852:Chromatography, Ion Exchange; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D010070:Oxalates / Q000494:pharmacology; D010072:Oxamic Acid / Q000494:pharmacology; D011796:Quinacrine / Q000494:pharmacology; D012242:Rhodobacter sphaeroides / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D010070:Oxalates; D007770:L-Lactate Dehydrogenase; D011796:Quinacrine; D010072:Oxamic Acid