L(+) lactate dehydrogenase activity from the electric organ of Electrophorus electricus (L.).
Properties of L(+) lactate dehydrogenase (LDH) of Electrophorus electricus (L.) electric organ were studied, comparing the substrates pyruvate and lactate. Electric organ LDH is a soluble enzyme with a pH optimum of 7.4 for pyruvate and 9.0 for lactate. The apparent Km was lower for pyruvate (Km = 2.5 X 10(-4) M) than for lactate (Km = 1.5 X 10(-2) M). With lactate as a substrate at pH 7.4, malonate, oxalate and pyruvate inhibited competitively. For pyruvate as substrate at pH 9.0 malonate inhibited non-competitively and oxalate shiwed uncompetitive inhibition. The different effects of the carboxylic acids on LDH activity suggest different stereospecificities of the two enzyme-coenzyme complexes in the forward and reserve reactions. The reactions of electric organ LDH with substrates and inhibitors are consistent with electrophoretic analysis suggesting that the enzyme is of the M-type.
D000818:Animals; D004593:Electrophorus / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*
D004791:Enzyme Inhibitors; D011768:Pyruvate Dehydrogenase Complex; D007770:L-Lactate Dehydrogenase