NAD+/NADP+-dependent malic enzyme: evidence of a NADP+ preferring activity in human skeletal muscle.
The L-malate NAD(P)+ oxidoreductase (decarboxylating) E.C.1.1.1.39 was purified from human skeletal muscle; the specific activity estimated in the presence of NAPD+ as coenzyme was approximately 15 mumol/min/mg. The apparent Vmax values for NAD+ (approximately 8 mumol/min/mg) and NADP+ (approximately 16 mumol/min/mg) show that the enzyme (in this tissue) is more active in the presence of NAPD+. This observation was confirmed by the estimation of enzymatic activity in competition experiments where both NAD+ and NADP+ were used together as coenzymes. The absence of pyruvate carboxylation and of oxalacetate decarboxylation activities demonstrates that the enzyme studied is E.C.1.1.1.39. In addition, the apparent Km values for NAD+ and NADP+ were calculated (15 and 0.05 mM, respectively). This paper provides the first demonstration of a NADP+ preferring activity of the enzyme in human skeletal muscle.
Liguori
M
M
Research Laboratory of Service of Neuromuscular Diseases, San Camillo Hospital, Rome, Italy.
Tessarolo
D
D
Abbruzzese
C
C
Giacanelli
M
M
D002262:Carboxy-Lyases / Q000378:metabolism; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000302:isolation & purification / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology*; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D011766:Pyruvate Carboxylase / Q000378:metabolism
D009243:NAD; D009249:NADP; D008291:Malate Dehydrogenase; C030574:malate dehydrogenase (decarboxylating); D002262:Carboxy-Lyases; C021916:oxaloacetate decarboxylase; D011766:Pyruvate Carboxylase