Studies on the appearance of soluble α-glycerophosphate dehydrogenase activity during the development of the sheep blowfly Lucilia

Abstract

1. 1.Early in the third instar, during larval development of Lucilia, α-glycerophosphate dehydrogenase activity per insect reached a peak corresponding to 12.5 per cent of the mature adult level. After puparium formation the activity per insect declined to about 2 per cent of the adult level. About 8 hours before adult emergence, the enzyme activity began to increase rapidly, rising tenfold in the next 2.3 days. Adult female flies were larger and contained more enzyme than males. Maximum enzyme activity was reached in the 4-day-old mature fly. In both 7-day-old male and female flies the enzyme activity began to decrease. 2. 2.The pattern of changes of the enzyme activity per mg. soluble protein (specific enzyme activity) over the life cycle was very similar to that of the enzyme activity per insect, except that the peak in mid-larval life was displaced forwards by 1 day and the magnitude of the increase over emergence was greater. This was a consequence of changes in soluble protein per insect, which increased fiftyfold in mid-larval life and declined by 42 per cent over the 8 hours spanning emergence. 3. 3.During the 4 days spanning adult emergence the specific enzyme activity increased eightfold in the head, two hundredfold in the thorax, and fourfold in in the abdomen. In newly emerged and 2-day-old flies 88 per cent and 95 per cent of the total enzyme activity was thoracic. 4. 4.Enzyme activity could not be elicited by mixing homogenates of insects of different ages. 5. 5.Cycloheximide at 1 μg. per insect inhibited by about 50 per cent the increase in specific enzyme activity of insects injected 3 hours before emergence and processed either at or a few hours after emergence. Cycloheximide injected into newly emerged flies produced inhibitions of 90 per cent over a 3-hour period. Inhibitions were always more pronounced for shorter periods of exposure to the inhibitor, regardless of when the insects were injected. 6. 6.Cycloheximide inhibited by about 30 per cent the decline in amount of soluble protein per insect over emergence; this inhibition persisted for longer periods than did that of enzyme formation.