Metabolic control analysis and enzyme variation: nutritional manipulation of the flux from ethanol to lipids in Drosophila.

The effect that variation in activities of the enzymes alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) has on the flux from 14C-ethanol to lipids was examined in third-instar larvae of Drosophila melanogaster and D. simulans. The activities of ADH and ALDH were also nutritionally manipulated by the inhibitor, cyanamide. Feeding larvae cyanamide before the flux test eliminated greater than 98% of the ALDH activity but only 40% of the ADH activity. The mean +/- SD flux control coefficient for ADH activity was 0.86 +/- 0.12, and that for ALDH activity was 0.02 +/- 0.07. This suggests that ADH is the major rate-limiting enzyme for the ethanol-to-lipid pathway in Drosophila larvae under the current experimental conditions.