MULTICATALYTIC PROTEINASE ACTIVITY IN TURTLE LIVER - RESPONSES TO ANOXIA STRESS AND RECOVERY

Activities of the multicatalytic proteinase complex (MPC) were detecte d in turtle (Trachemys scripta elegans) liver. The ratio of peptidylgl utamyl-peptide bond hydrolyzing, trypsin-like, and chymotrypsin-like a ctivities was 6:2.7:1 for the MPC partially purified by Sepharose CL-6 B gel filtration. Molecular mass of the turtle liver enzyme was 940 +/ - 46 kD. Nondenaturing PAGE revealed a single band containing MPC acti vity reacting with peptide substrate. In vivo anoxia exposure (20 h su bmergence in N-2-bubbled water) and subsequent 24 h aerobic recovery s timulated changes in liver protease activity. Peptidylglutamyl-peptide bond hydrolyzing activity of the partially purified MPC increased by 29% during aerobic recovery. Elevated MPC activity during recovery may serve to catabolize specific stress-related proteins or to remove pro teins damaged by oxygen free radicals generated upon the reintroductio n of oxygen.