POTASSIUM IODIDE-INDUCED CHANGES IN PYRUVATE-DEHYDROGENASE COMPLEX FROM BACILLUS-STEAROTHERMOPHILUS

Treatment with KI and its subsequent removal induced disassembly of Ba cillus stearothermophilus pyruvate dehydrogenase complex (PDC) and ass ociation of disassembly products, respectively, The disassembly yielde d neither completely dissociated components nor aggregate, but did yie ld a few molecular forms smaller than PDC. Depending on the KI concent ration, these changes were of three phases: K-l, below 0.6 hr; K-2, 1. 0-1.5 ni; K-3, above 1.8 M. PDC was disassembled in K-l to C1 comprisi ng pyruvate decarboxylase and lipoate acetyltransferase mainly and C2 comprising the decarboxylase and dihydrolipoamide dehydrogenase. In K- l, the removal of KI resulted in an apparent reconstitution of PDC. Th e mixing of C1 with an excess of C2 yielded an assembly larger than PD C and restored enzyme activities, but specific activities were differe nt from those of PDC. In K-2 and K-3 phases, complexes smaller than PD C were yielded from disassembly products, and activities except for th at of the acetyltransferase were not restored.