Nicotinamide-adenine dinucleotide-linked "malic" enzyme in flight muscle of the tse-tse fly (Glossina) and other insects.
1. A high activity of NAD-linked "malic" enzyme was found in homogenates of flight muscle of different species of tse-tse fly (Glossina). The activity was the same as, or higher than, that of malate dehydrogenase and more than 20-fold that of NADP-linked "malic" enzyme. A similar enzyme was found in the flight muscle of all other insects investigated, but at much lower activities. 2. ACa2+-stimulated oxaloacetate decarboxylase activity was present in all insect flight-muscle preparations investigated, in constant proportion to the NAD-linked "malic" enzyme. 3. A partial purification of the NAD-linked "malic" enzyme from Glossina was effected by DEAE-cellulose chromatography, which separated the enzyme from malate dehydrogenase and NADP-linked "malic" enzyme, but not from oxaloacetate decarboxylase. 4. The intracellular localization of the NAD-linked "malic" enzyme was predominantly mitochondrial; latency studies suggested a localization in the mitochondrial matrix space. 5. Studies on the partially purified enzyme demonstrated that it had a pH optimum between 7.6 and 7.9. It required Mg2+ or Mn2+ for activity; Ca2+ was not effective. The maximum rate was the same with either cation, but the concentration of Mn2+ required was 100 times less than that of Mg2+. Acitivity with NADP was only 1-3% of that with NAD, unless very high (greater than 10mM) concentrations of Mn2+ were present. 6. It is suggested that the NAD-linked "malic" enzyme functions in the proline-oxidation pathway predominant in tse-tse fly flight muscle.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002262:Carboxy-Lyases / Q000378:metabolism; D002848:Chromatography, DEAE-Cellulose; D006863:Hydrogen-Ion Concentration; D007313:Insecta / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008291:Malate Dehydrogenase / Q000302:isolation & purification / Q000378:metabolism*; D008345:Manganese / Q000494:pharmacology; D008931:Mitochondria, Muscle / Q000201:enzymology; D009132:Muscles / Q000201:enzymology*; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D014370:Tsetse Flies / Q000201:enzymology*
D009243:NAD; D008345:Manganese; D009249:NADP; D008291:Malate Dehydrogenase; D002262:Carboxy-Lyases; D008274:Magnesium; D002118:Calcium