CHANGES IN THE ACTIVITY OF DOPA QUINONE IMINE CONVERSION FACTOR DURING THE DEVELOPMENT OF BOMBYX-MORI

The activity of DOPA quinone imine conversion factor (QICF) in tissues at different developmental stages of the silkworm, bombyx mori, was determined. QICF activity was detected in all developmental stages from egg to pupa although the activities, other than in fifth instar larvae, were quite low. Activity in whole larvae peaked one day before the onset of larval-pupal development and declined to a low level shortly before ecdysis. In whole pupae, maximal QICF activity was obtained 1 h after pupation. The activity in larval cuticles was elevated on the last day of the fourth instar and again between days 4 and 8 of the fifth instar, decreasing to very low levels before pupal ecdysis. QICF was detectable in pupal cuticles with most of the pupal activity found in homogenates of mid and hind guts. A major part of the total larval QICF activity was found in hemolymph. Activity in hemolymph varied in a different manner from that in cuticles, with markedly raised levels immediately before pupal ecdysis when the cuticular activity had decline. It is postulated that QICF in cuticles plays some role in wound healing and/or sclerotization, while QICF in hemolymph participates in melanization in the humoral immune system.