A comparative study of the spicule venom of Euproctis caterpillars.

Caterpillar spicule venoms were extracted and studied for the following activities: arginine ester (BAEE) hydrolase, tyrosine ester (ATEE) hydrolase, protease (casein digestion) and phospholipase A (indirect hemolytic activity). Crude spicule venom of E. chrysorrhoea preferably hydrolyzed BAEE in contrast to E. subflava venom, which hydrolyzed ATEE in preference to BAEE. This difference was confirmed by Sephadex G-100 elution profiles. The esterase activity in E. chrysorrhoea venom was separated into two peaks with average mol. wts. of 96,000 and 44,000. The first peak demonstrated optimal BAEE hydrolysis at pH 8.6 and 37 degrees C, whereas the second peak optimally hydrolyzed both BAEE and ATEE at pH 8.45 and pH 8.6 at 45 degrees C respectively. The esterase activity in E. subflava venom was separated into two peaks with average mol. wts of 63,000 and 32,000 showing optimal hydrolysis of BAEE at pH 8.9 and 37 degrees C, and of ATEE at pH 7.75 and pH 8.5 at 40 degrees C. The column fractions showed comparable proteolytic activity, irrespective of differences between their esterase activities. The presence of phospholipase A (PLA) enzyme in crude spicule venom of both species was evident from their indirect hemolytic activities. The PLA activity eluted with the void volume and seems to be associated with some high molecular weight protein. Under the assay conditions used, E. subflava venom contained 50-100 times less PLA activity than E. chrysorrhoea venom.