title: Regulation of aerobic fermentation in Leishmania donovani promastigotes by NADP+-dependent malic enzyme.
abstract: NADP+-dependent malic enzyme (decarboxylating) was extracted from Leishmania donovani promastigotes with Triton X-100. The enzyme was specific for NADP+ and did not decarboxylate oxaloacetate (OA). The substrate activity relationship was hyperbolic for both L-malate and NADP+, and Km values were calculated as 0.18 and 0.12 mM, respectively. The enzyme exhibited a broad pH optimum of 7.5-8.0. Pyruvate, NADPH and OA inhibited the reaction in a competitive manner with apparent Ki values of 0.2, 0.04 and 0.04 mM, respectively, while oxalate inhibition was of the mixed type. The kinetic results obtained indicate that malic enzyme is involved in the regulation of carbon flow towards aerobic fermentation, complete oxidation of dicarboxylic acids or biosynthetic purposes.
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003653:Decarboxylation; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007893:Leishmania donovani / Q000201:enzymology*; D008291:Malate Dehydrogenase / Q000502:physiology*; D009249:NADP
chemical_list: D009249:NADP; D008291:Malate Dehydrogenase