[On molecular biology of aging. 11th communication. Enzyme adaptation, age (author's transl)].

Age-dependent modifications of enzyme adaptations in response to a variety of environmental alterations are a biochemical expression of biological ageing. In this paper age-dependent changes of the adaptation of a number of enzymes are described. Experiments from our laboratory indicate that pyruvate kinase is more responsive to starvation and refeeding in young animals. The diminished response of pyruvate kinase in old age is caused by a decreased adaptability of the regulatory isoenzyme PK-L.