Effects of hibernation on multicatalytic proteinase complex in thirteen-lined ground squirrels, Spermophilus...

Multicatalytic proteinase complex (MCP) was studied in skeletal muscle of the hibernating ground squirrel, Spermophilus tridecemlineatus. MCP was partially purified using a S-400 gel filtration column and Centricon concentrating devices and assayed fluorometrically using three AMC-labeled substrates. K(m) and V(max) values were determined for each substrate with no significant differences between the enzyme from euthermic versus hibernating animals when assayed at 23 degrees C. However, properties of MCP from euthermic and hibernating ground squirrels were differentially affected by low assay temperature (8-10 degrees C) and also differed from the mouse enzyme, the data indicating that ground squirrel MCP is better suited for low temperature function. MCP preferentially degrades oxidatively-damaged proteins and quantification of protein carbonyl content showed that the level of oxidatively-damaged protein in skeletal muscle decreased by > 75% during hibernation suggesting a continuing role for the MCP in the torpid state.