1. Ox liver glutamate dehydrogenase is activated by bovine pancreatic alpha-chymotrypsin, but the extent of activation is dependent on the age of the dehydrogenase preparation. 2. The degree of activation is constant and the pseudo-first-order rate constant of activation is directly proportional to the concentration of proteinase used. 3. Commercial preparations of alpha-chymotrypsin differ in their ability to produce a secondary inactivation phase, and this was shown to be due to low tryptic contamination. The ‘superactive’ form of glutamate dehydrogenase has an increased sensitivity to tryptic inactivation as compared with the native enzyme. 4. Analysis of the activation by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis revealed that the subunit molecular weight of ‘superactive’ glutamate dehydrogenase differs by less than 5% from that of the native subunit.
