The in vitro conversion of a specific molecular form of glucose 6-phosphate dehydrogenase from Musca domestica L.

A nicotinamide adenine dinucleotide phosphate dependent glucose 6-phosphate dehydrogenase (G6PD), belonging to type I of Kamada and Hori's classification, is present on the zymograms of newly emerged males of Musca domestica. It is capable of undergoing tryptic degradation and being thus transformed into a different active enzymatic form, with some of its catalytic properties unchanged, but with different electrophoretic mobility. We show in this paper that this specific G6PD form of gut origin in M. domestica is not a tissue-specific enzyme, but rather a product of hydrolytic degradation by gut proteinases which act during the process of homogenization. Besides, the G6PD of type I in the housefly is shown to be sensitive to the "storage effect" and to protection by mercaptoethanol, contrary to its hydrolytic gut form which is not sensitive to these processes. In this connection, we discuss the possible reasons for these differences in behavior.