| Abstract: | The alpha-ketoglutarate dehydrogenase complex from Escherichia coli catalyzes the hydrolysis of S-succinyl-CoA to succinate and CoASH. The reaction rate is dependent upon the presence of thiamin pyrophosphate and NADH, as well as the functional integrity of the alpha-lipoyl groups associated with the enzyme. The Km value for S-succinyl-CoA is 9.3 X 10(-5) M, and the maximum velocity is 0.02 mumol X min-1 X mg of protein-1 at pH 7 and 25 degrees C. This hydrolysis can be rationalized on the basis that succinyl thiamin pyrophosphate is generated under reductive succinylation conditions. Occasional diversion of succinyl thiamin pyrophosphate to hydrolysis produces succinate. |
