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Comparative studies on the activities of isocitrate lyase (ICL) and malate synthase (MS) were carried out with Saccharomycopsis lipolytica incubating the yeast on media with different carbon sources. When cells were incubated in minimal medium with glucose, the activities of both enzymes were very low. In contrast, in minimal medium with acetate enhanced enzyme activities could be demonstrated. It is probably that the synthesis of ICL is repressed in presence of glucose. Furthermore the activity of ICL was inhibited by tricarboxylic acid cycle intermediates like succinic acid and oxalacetic acid. It was concluded that the syntheses of enzymes are derepressed. When cells of Sm. lipolytica were incubated in minimal medium with acetate, a high enzyme activity is evident. Synthesis of ICL on acetate was inhibited by cycloheximide and actinomycin D. The results were discussed comparing them with data obtained from other organisms.

In contrast to 3 months old rats of the Wistar strain show 18 months old animals an elevation of the serum triglyceride level under the conditions of a sucrose diet (25% of the energy uptake). Clinical investigations with women show a similar age difference. These results may not be explained by the age-dependent behavior of the activity of several lipogenic enzymes of liver and adipose tissue and of their adaptation to a sucrose diet, but the age-dependent decrease of the lipoprotein lipase activity may be of special importance.