STUDIES ON MAMMALIAN AND HUMAN PYRUVATE AND ALPHA-KETOGLUTARATE DEHYDROGENATION COMPLEXES
Rept. no. 1 (Final), 15 Mar 1965-14 Mar 1966
NAGASAKI UNIV (JAPAN) ATOMIC DISEASE INST
Pagination or Media Count:
A coenzyme A- and NAD-linked pyruvate and alpha-ketoglutarate dehydrogenase complexes have been isolated from pig heart muscle as multienzyme units with molecular weights of approximately 9 and 2.7 million, respectively. Pyruvate dehydrogenase complex contains approximately 67 moles of protein-bound lipoic acid and 17 moles of bound FAD. Alpha-ketoglutarate dehydrogenase complex contains approximately 10 moles of protein-bound lipoic acid, 9 moles of FAD and 6 moles of thiamine-PP. Both complexes were activated by Ca2 as the same extent as Mg2 which had been considered as one of the typical metal activators of oxidative decarboxylation reaction of alpha-keto acid. These activating effects were in good agreement with the results of the metal contents obtained by the atomic absorption analysis. Pyruvate dehydrogenase complex was strongly inhibited by EDTA at low concentration, but on the contrary, alpha- ketoglutarate dehydrogenase complex was little inhibited by EDTA and rather obviously inhibited by 8-hydroxyquinoline. Attempts have been made to dissolve both complexes into three essential components containing each coenzyme, but it did not still go well to restore pyruvate decarboxylase activity. Two other components, lipoic reductase-transacetylase and lipoamide dehydrogenase, were isolated in pure status. Preliminary experiments to determine the structural organization of the mammalian pyruvate and alpha-ketoglutarate dehydrogenase complexes have been made and hopeful results were obtained.