Biomedical subjects
Publications and source records attributed to V Richter.
We determined the synthesis of fatty acids in rat liver in vitro, using the method of labeling the fatty acid with tritiated water. After the well-known increase of the biosynthesis of fatty acids in the postnatal period we found an age-dependent decrease which is positively correlated with the activity of lipogenic enzymes of rat liver.
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.
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.
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The activities of lipogenic enzymes of the lung of female rats of the Wistar strain were measured in the age groups 3, 18, 21, 25, and 30 months. The activities of malic enzyme (EC. 1.1.1.40) and citrate cleavage enzyme (EC. 4.1.3.8) decrease in dependence on aging. In contrast, the enzymes of pentose phosphate shuttle glucose-6-phosphate dehydrogenase (EC. 1.1.1.49) and 6-phosphogluconate dehydrogenase (EC. 1.1.1.44) do not show an age dependence.