Novel NADP-linked isocitrate dehydrogenase present in peroxisomes of n-alkane-utilizing yeast, Candida tropicalis: comparison with mitochondrial NAD-linked isocitrate dehydrogenase.
Peroxisomal NADP-linked isocitrate dehydrogenase (Ps-NADP-IDH) was purified for the first time from Candida tropicalis cells grown on n-alkane as a carbon source, which was effective in proliferation of peroxisomes. The properties of Ps-NADP-IDH were compared with those of mitochondrial NAD-linked isocitrate dehydrogenase (Mt-NAD-IDH) purified from the cells grown on acetate, in which peroxisomes did not proliferate. Ps-NADP-IDH was a homodimer of identical subunits (45 kDa), while Mt-NAD-IDH was suggested to be a heterooctamer composed of two types of subunits with different molecular masses (41 and 38 kDa). Kinetic studies revealed that Ps-NADP-IDH gave Michaelis-Menten saturation curves against isocitrate and NADP concentrations, whereas Mt-NAD-IDH was an allosteric enzyme regulated by ATP, AMP, and citrate. Inhibition by 2-oxoglutarate, a precursor of glutamate, was observed only for Ps-NADP-IDH. Both enzymes were inhibited by concomitant addition of oxalacetate and glyoxylate. The function of Ps-NADP-IDH seems to be completely discriminated from that of Mt-NAD-IDH as reflected by their distinct subcellular localizations. Furthermore, the properties of Ps-NADP-IDH were also compared with those of other mitochondrial and cytosolic IDHs from sources reported previously.
Yamamoto
S
S
Department of Synthetic Chemistry and Biological Chemistry, Faculty of Engineering, Kyoto University, Japan.
Atomi
H
H
Ueda
M
M
Tanaka
A
A
D000085:Acetates / Q000378:metabolism / Q000494:pharmacology; D000473:Alkanes / Q000378:metabolism; D002175:Candida / Q000201:enzymology*; D006038:Glyoxylates / Q000494:pharmacology; D007521:Isocitrate Dehydrogenase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008830:Microbodies / Q000201:enzymology*; D008928:Mitochondria / Q000201:enzymology*; D008970:Molecular Weight; D011487:Protein Conformation
D000085:Acetates; D000473:Alkanes; D006038:Glyoxylates; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+); C031150:glyoxylic acid