Esterase-2 in Ephestia kühniella. II. Tissue-specific patterns

Expression of esterases during ontogenesis of the flour beetle Tribolium castaneum (Tenebrionidae; Coleoptera)

Two electrophoretically fast-migrating, nonspecific esterases were detected in two strains of the flour beetle Tribolium castaneum and designated F (fast) and S (slow) according to their relative migration distances. Both isozymes are associated with the alimentary canal and display ontogenetic changes. Their activity is very low in the egg stage, increases in the larva, and declines dramatically in the pharate pupa and pupa. The overall activity in the pupal stage is low, yet increases gradually throughout this period. In the adult, the activity of the esterases rises sharply. The larval and adult F and S isozymes were found to hydrolyze alpha- and beta-naphthylacetate and alpha-naphthylpropionate with almost equal capacity. alpha-Naphthyl laurate was cleaved by the F enzyme of both larvae and adults. The F and S were insensitive to inhibitors of arylesterases and cholinesterases and were markedly inhibited by the organophosphate di-isopropylphosphorofluoridate (DFP) and could be classified as carboxylesterases. Differential sensitivities of larval and adult esterases to urea and heat treatment as well as to DFP may indicate the expression of different genes during metamorphosis.

Variants of alpha-glycerophosphate dehydrogenase in diploids and triploids of Drosophila melanogaster

On the basis of band staining intensities in electrophoretic runs of single flies homozygous and heterozygous for two alleles at the autosomal locus for GPDH, F allele activity is believed to be 8% lower than S allele activity. Indeed, the intensity distribution in the patterns of FSS and FFS triploid females shows that both are not equally expressed. On a per fly or live weight basis, females with two and three doses of the Gpdh gene show bands with equal staining intensity, thus exhibiting a dosage effect when GPDH activity is estimated on a per cell basis.