Diet-induced alterations in distribution of multiple forms of alcohol dehydrogenase in Drosophila

Abstract

IT is now well accepted that enzyme polymorphisms are widespread among organisms. Electrophoretic polymorphisms in particular have been extensively studied and discussed¹. One enzyme, alcohol dehydrogenase (ADH) has received special attention because the relative proportions of two polymorphic forms (allozymes), Adh^F and Adh^s, in Drosophila, seem to vary with environmental temperature^2,3. The situation with regard to Drosophila ADH, however, is complicated by the fact that even in flies homozygous for a given electrophoretic variant or allozyme, three forms of ADH activity are observed after electrophoresis^4–6. They are distributed in such a way that (on agar gel electrophoresis) the one which migrates most cathodally (termed ADH⁵ in the Adh^F strain) has the highest activity, but is the least stable to heat. The least cathodally migrating form (ADH¹ in the Adh^F strain) has the least activity and is the most heat stable, whereas the third form (ADH³ in the Adh^F strain) is intermediate with respect to both activity and heat stability (Fig. 1a). These forms are termed isozymes, in order to contrast them with the allozymes described above.