Diabetes Increases Active Fraction of Branched-Chain 2-Oxoacid Dehydrogenase in Rat Brain

Conditions were developed to permit the extraction of branched-chain 2-oxoacid dehydrogenase from brain tissue in the state of phosphorylation in which it occurred in vivo. Tissue was cold clamped to prevent interconversion of the enzyme forms without rupturing mitochondrial membranes. Extraction was carried out in the presence of NaF to prevent dephosphorylation of the enzyme complex and in the presence of ADP to prevent phosphorylation. In adult male control rats, ∼35% of the total enzyme from brain was present in the active form. In brains of diabetic rats, the active fraction was increased to 56%. Total activities did not differ in the two groups of rats.