[On moleculare biology of ageing. 10th communication. Enzyme level, age (author's transl)]

The intracellular enzyme level is a function of both the rate of synthesis and the rate of degradation. During aging the levels of a number of enzymes in various animal organs have been found to change; some increase, others decrease. These age dependent changes in enzyme levels may be the result of an alteration in either the rate of enzyme synthesis, or of enzyme degradation or both. The degradation rate constants and the half-life times of citrate cleavage enzyme and glucose-6-phosphate dehydrogenase are uneffected by age, whereas the enzyme levels decrease. Thus the decreased enzyme levels in the liver of old rats can be ascribed to a diminished rate of enzyme synthesis. The half-life time of malic enzyme decreases in dependence of age and the increased enzyme degradation contributes to the diminished enzyme level in the liver old rats.