Age related activity changes in arginine phosphokinase in the house fly, Musca domestic+ L

The activity of ATP; L-arginine phosphotransferase (E.C.2.7.3.3.), was shown to exhibit age-dependent changes in both male and female house fly. Enzyme activity demonstrated more marked changes in the male than in the female, increasing 44-fold from emergence to a peak at 2 days of age and thereafter declining, at first sharply then gradually to a value at 14 days of age, representing a third of the activity found at the peak. Activity in the female fly also showed a peak at 2 days of age, which thereafter declined, although more gradually than was observed in the male. Activity changes expressed on a per fly or wet weight bases were nearly identical. Age-related activity changes on a milligram protein basis demonstrated similar increases; however, the percentage decrease from the 2-day peaks were less striking, although highly significant. No kinetic or physical changes in the enzyme were detected, nor could any soluble inhibitors or activators of enzyme be identified. The changes in arginine phosphokinase activity fall into a sequential pattern of enzyme changes, reflecting an apparently ordered mechanism underlying a decline in flight ability in this species.