| Abstract: | Proteolytic processing of the vitellin in Blattella germanica eggs occurs 4 days postovulation and is correlated with both the onset of its utilization and the major portion of the embryo's growth. Yolk phosphatase is also expressed coincident with this event, and some aspects of its activation have been investigated. The enzyme is absent from the ooplasm (yolk) during the first 2 days following ovulation but increases approximately 20-fold in specific activity between days 3 and 4, when assayed at pH 3.9 or 4.8 and 9-fold at pH 6.5. No activation is observed for yolk-bound α-mannosidase, its specific activity remains elevated through the first 6 days following ovulation. This suggests that expression of the phosphatase is regulated independently of that of α-mannosidase in the yolk. Yolk with active phosphatase can dephosphorylate native vitellin, delipidated vitellin, and phosphocasein. Sucrose density gradient centrifugation of yolk obtained from eggs 4 days postovulation, revealed that phosphatase activity cosediments with material which reacts with antivitellin antibodies, while α-mannosidase and β-N-acetyl glucosaminidase are found near the top of the gradient. Oothecae derived from crossing certain translocational heterozygote males and wild-type females contain some eggs with severely depressed levels of yolk phosphatase in which embryos do not grow. Vitellin in these eggs fails to undergo proteolytic processing as late as day 5 postovulation and retains the subunit composition of freshly ovulated vitellin. |
