JBC, Vol. 250, Issue 16, 6351-6354, Aug, 1975
Alpha-methylisocitrate. A selective inhibitor of TPN-linked isocitrate dehydrogenase from bovine heart and rat liver
G. W. Plaut, R. L. Beach and T. Aogaichi
Alpha-Methylisocitrate (3-hydroxy-1,2,3-butanetricarboxylate) is a potent
inhibitor, competitive with isocitrate
(1-hydroxy-1,2,3-propanetricarboxylate), of the TPN-linked isocitrate
dehydrogenase from bovine heart and rat liver; it does not inhibit the
DPN-specific enzyme from these tissues. In the presence of magnesium ion,
values of Kis for DL-alpha-methylisocitrate for purified bovine heart
enzyme, rat liver cytosol, and rat liver mitochondrial extract were in the
range of 0.1 muM to 0.3 muM. This compared to values of apparent Km for
DL-isocitrate for the same tissue preparations of 14 muM to 20 muM. One of
the DL isomer pairs of alpha-methylisocitrate was inactive; the
observations suggest that it is threo-alpha-methylisocitrate which inhibits
TPN-linked isocitrate dehydrogenase. A method of synthesis of
DL-threo-alpha-methylisocitric lactone
(2-methyl-5-oxo-2,3-furandicarboxylic acid) from dimethyl
trans-epoxymethylsuccinate and dimethylmalonate is described.