Alterations in the sensitivity to endogenous proteolysis due to storage of fructose-1,6-bisphosphatase extracts of liver and muscle of young and old rats.

The sensitivity of fructose-1,6-bisphosphatase (FBPase: EC 3.1.3.11) to endogenous proteolysis was studied in liver and muscle extracts of young (28 weeks) and old (97 weeks) rats (stored at 4 degrees +/- 2 degrees C) by monitoring the alterations in its properties. Apart from the level of total enzyme activity, decrease in activity ratio (at pH 7.0/9.2) and sensitivity to AMP inhibition no age-dependent significant change was found during storage of the liver extract. However, a more significant increase in activity, comparatively less decrease in activity ratio, and retention of sensitivity to AMP inhibition were observed during the storage of muscle enzyme extract from old rats than from young rats. Using gel electrophoresis, an extra degradative active product was observed in all samples except those of old rat muscle. These results may indicate tissue-specific alterations in the susceptibility of FBPase to endogenous proteolysis during old age in the rat.