Activation of grass carp liver alcohol dehydrogenase by limited proteolysis

Limited proteolysis of grass carp alcohol dehydrogenase by alkaline protease or subtilisin BPN' at 30 degrees C for 6 hr generated a nicked species that was catalytically active. Electrophoresis on a denaturing SDS-PAGE showed that the 40 kDa subunit of the intact enzyme was cleaved to produce subunits of 27 and 13 kDa, which remained tightly associated with each other under native condition. Such a proteolytically nicked form was catalytically more active than the original intact form of the enzyme. The Vmax value toward the oxidation of ethanol at pH 10 increased by 7.8 fold whereas the K(m) value also exhibited a 140 fold increase. On the other hand, when the same protease treatment was applied to horse liver alcohol dehydrogenase, no activation nor any specific cleavage can be observed.