Adaptation of Drosophila enzymes to temperature IV. Natural selection at the alcohol-dehydrogenase locus

Studies were carried out on the temperature-dependent kinetic properties (K_m, Q₁₀, E_a, thermostability) of alcohol-dehydrogenase allozymes from D. melanogaster. It was shown that there is a parallelism between the biochemical properties of the enzymes and the behaviour of the genes in natural and cage populations. Furthermore, the relationship between the temperature-dependent kinetic properties of alcohol dehydrogenase and assay temperature was examined in three tropical and two temperate Drosophila species. K_m patterns were similar among species from the same habitat and different between habitats. No such parallelism was seen with respect to thermal inactivation. The Q₁₀ values in general reflected temperature-dependent changes in K_m. It is discussed that the mechanistic connection observed between the biochemical and population levels (intra-and interspecifically) strongly suggests that temperature acts as a selective factor on the structural Adh locus in the genus Drosophila.