Choriolysin H

Publisher Summary This chapter discusses the activity, specificity and structural chemistry of choriolysin H. Choriolysin H hydrolyzes the inner layer of egg envelope and releases unique proline-rich polypeptides from it. As a result of hydrolysis by choriolysin H, the inner layer of egg envelope is swollen. The released polypeptides consist of repeats of Pro-Xaa-Yaa, mainly Pro-Glu-Yaa, which are present in ZI-1,2, one of the major subunit proteins of the egg envelope. The pH optimum is about 8.0 and 8.7 for caseinolytic activity and choriolytic activity, respectively. Both activities are inhibited by EDTA at a concentration of ImM, but are not inhibited by DFP, iodoacetamide or iodoacetic acid. The enzyme contains zinc, calcium and magnesium as revealed by metal analysis. Choriolysin H tends to bind tightly to the egg envelope. One of the antichoriolysin H monoclonal antibodies does not affect caseinolytic activity, but inhibits both choriolytic activity and binding to the egg envelope. The choriolysin H genes are multicopy genes and lack introns. Six of seven HCE genes cloned are situated in a cluster and arranged in tandem. A putative promoter region of each gene contains a TATA box sequence, but neither a CAT box nor GC box sequences.