An aspartic proteinase in Drosophila: maternal origin and yolk localization

An aspartic proteinase activity has been found in Drosophila oocytes and embryos. The proteinase is maximally active at pH 3.5 and has been characterized by its sensitivity to specific inhibitors and by the specificity of cleavage. The activity is very low and has been localized in the yolk granules. The proteinase is detected in mature oocytes (i.e., it is of maternal origin) and remains essentially constant during embryogenesis. This suggests that the Drosophila aspartic proteinase functions mainly before embryogenesis.