Adaptive significance of amylase polymorphism in Drosophila--VI. Properties of two amylase variants and the effect of food components on amylase activity in Drosophila subobscura.

1. Properties of amylase from two D. subobscura strains homozygous for two different amylase variants (AmyS and AmyF) were determined. 2. Amylase of both strain adults showed a pH optimum of 7.8. 3. The AmyF enzyme showed a higher thermostability. 4. They differed in both maximum activity and Michaelis constant (Vmax of 6.25 and 3.45, Km of 0.7% and 0.42% starch for AmyS and AmyF, respectively). 5. The effect of different feeding conditions in amylase activity in the above Drosophila strains was also studied. Amylase activity was always detected but to a different level depending on diet composition.