ENZYMES IN ONTOGENESIS (ORTHOPTERA)

XVIII. ESTERASES IN THE GRASSHOPPER EGG

¹ From the Zoölogical Laboratories, State University of Iowa

1. Glycerol extracts of the grasshopper egg (Melanoplus differentialis) have been tested for hydrolytic activity on methyl butyrate, tributyrin and olive oil during various stages in the development of the egg. The ability to hydrolyze methyl butyrate is high when the egg is laid; this value declines between the tenth and fifteenth day of development, remains constant during diapause and slowly declines again during the post-diapause period. The action of extracts on tributyrin is much stronger, remains constant from the time of laying until the cessation of the diapause and then declines markedly. No action on olive oil could be demonstrated.

2. Optimum activity in hydrolysis of tributyrin is at pH 6; the activity of the enzyme reacting with methyl butyrate is only slightly affected by changes in the H-ion concentration.

3. Temperature affected the methyl butyrinase and tributyrinase activity in a different manner. Exposure to tempetatures above 55° C. depressed the activity of the former while the activity of the latter persisted to 65° C.

4. The hydrolytic action on tributyrin increased with temperature between 5° and 25° C. and declined at higher temperatures. Methyl butyrinase activity increased with temperature between 0° and 45° C.

5. The esterases seemed to be associated with the yolk until just before hatching.

6. The effect of sodium oleate, calcium ion and various inhibitors of lipolytic enzymes on the extracts used were determined.