Amylase variants in Drosophila melanogaster: Linkage studies and characterization of enzyme extracts

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Abstract
The amylases of D. melanogaster were characterized by several parameters. Starch‐iodine and 3,5‐dinitrosalicylic acid reduction methods were employed to determine activity. Conditions were defined under which activity, in crude aqueous extracts could be restricted to α‐amylase(s) of fly origin. Biochemical properties of the α‐amylases from eleven homozygous Amy strains were found to be very similar in temperature stability, pH optimum, substrate specificity and the effects of various activators and inhibitors. All were activated by chloride ions and showed a pH optimum of about 7.4. Relative efficiencies on several substrates were tested: soluble starch, amylopectin, β‐limit dextrins, glycogen and amylose. EDTA completely inhibited all extracts, presumably by the removal of calcium required for activation. The specific α‐amylase inhibitor from wheat grain also completely inhibited activity, as did reduced glutathione. PCMB had no discernible effects on activity.Eight of the 11 strains tested are known to produce different electrophoretic banding patterns for amylases. The total maximum activity of each strain may also be used to characterize it and, accordingly, three strains with amylases of the same electrophoretic mobility were distinguished by differences in their specific activities. Sexual dimorphism in amylase activity was defined, as well as activity in heterozygotes between strains. Aside from the distinctions between strains already noted, four strains differed in their relative susceptibility to heat and to α‐amylase inhibitor.Linkage experiments indicated that the Amy region lies at 77.3 on the genetic map of the second chromosome and to the right, but near, section 52F on the salivary chromosome map.