The localization of a particle-bound tyrosine activating enzyme in Lucilia cuprina and the distribution of free amino acids during the life cycle

Regulation of glutamine metabolism during the development of Bombyx mori larvae

Waste ammonia is re-assimilated into amino acids via the amide group of glutamine and the amino group of glutamate (i.e. through glutamine synthetase/glutamate synthase pathway) for silk synthesis in the silkworm, Bombyx mori, in the last larval stadium. Glutamine concentration in hemolymph gradually decreased with the progress of the fifth instar and it remained at very low levels during the spinning stage, then followed by a sharp increase at the larval-pupal ecdysis. The changes in glutamine synthetase (GS) activity in silkworm tissues were relatively small through the larval development, while the changes in glutamate synthase (GOGAT) activity, especially in the posterior silk glands, were more drastic. In addition, activities of GOGAT in the tissues were much higher than those of the other enzymes involved in glutamine utilization, suggesting that glutamine pool was regulated mainly by the changes in GOGAT activity. Western blot analysis indicated that the changes in GOGAT protein level correlated with the changes in GOGAT activity. Topical application of a juvenile hormone analogue, methoprene, induced an accumulation of glutamine in the hemolymph of the fifth instar larvae. The levels of GOGAT protein and activity in the tissues of the methoprene treated larvae were much lower than those of the control larvae, whereas the methoprene treatment had no effect on the levels of GS activity. In conclusion, GOGAT expression promoted by reduction of juvenile hormone titer is quite important for enhanced utilization of nitrogen for synthesis of silk protein during the last larval instar.

Aspects of the development of flight-muscle sarcosomes in the sheep blowfly, Lucilia cuprina, in relation to changes in the distribution of protein and some respiratory enzymes during metamorphosis

1. Changes in the amounts and distribution of protein and respiratory enzymes have been estimated during the life cycle of the fly Lucilia cuprina. 2. The fully fed larva contains about 7mg. of protein, the pupa and newly emerged fly about 4mg., and the mature adult about 3mg. 3. There are two periods of incorporation of protein into particles at the expense of the soluble protein; the first, immediately after pupation, may store protein (0.5mg./insect) for use in adult development; the second, over the period of emergence, was due mainly to the development of the thoracic mitochondria of the adult (0.7mg./insect). 4. In the thorax, cytochrome c oxidase and the dehydrogenases for glycerophosphate, isocitrate (NAD-dependent), succinate and malate appeared initially in small particles (less than 1mu in diameter). 5. In adult development these enzymes were redistributed so that in the mature fly most of the activity was present in larger particles (1-10mu in diameter). 6. During this redistribution the specific activity (mul. of oxygen/hr./mg. of protein) of glycerophosphate dehydrogenase in the small particles was 690 at 1(1/2) days before emergence, 955 at emergence and 980 at 7 days after emergence; the corresponding values for the large particles were 164, 760 and 1220. 7. In the mature fly the highest specific activities (mul. of oxygen/hr./mg. of protein) estimated were: glycerophosphate dehydrogenase 1380, isocitrate dehydrogenase (NAD-dependent and requiring ADP and Mg(2+)) 408, succinate dehydrogenase 122, malate dehydrogenase 190, and cytochrome c oxidase 1360. 8. The results are considered in relation to the development of the flight-muscle sarcosomes.