Thermal Disassembly of Pyruvate Dehydrogenase Multienzyme Complex from Bacillus stearothermophilus

Abstract

Thermostabilities of component enzymes in the pyruvate dehydrogenase complex from Bacillus stearothermophilus decreased in the order lipoamide dehydrogenase, lipoate acetyltransferase, and pyruvate decarboxylase (E1). Fluorescence of an extrinsic 8-amino-1-naphthalenesulfonate (ANS) increased with inactivation of E1. The thermal denaturation of the enzymes resulted in disassembly of the complex. E1 was involved in a resulting aggregate of the complex. The interaction between ANS and denatured E1 accounted for an increase in fluorescence.