164 - Choriolysin L

Abstract

This chapter elaborates the activity, specificity and structural chemistry of choriolysin L. Choriolysin L displays very low choriolytic activity when examined by the turbidimetric method. It hardly digests the intact inner layer of egg envelope, but efficiently digests the swollen inner layer of egg envelope prepared by a limited digestion by choriolysin H. The specificity of choriolysin L is 8,000 and 100,000 times greater than those of trypsin and thermolysin, respectively. The hatching of medaka embryos results from a two-step digestion of the two enzymes; choriolysin H swells the inner layer of egg envelope by limited digestion, and choriolysin L solubilizes the swollen part of it completely. Choriolysin L also hydrolyzes casein and some synthetic substrates such as Suc-Leu-Leu-Val-Tyr-fNHMec . The pH optimum is about 8.6 for caseinolytic activity. Choriolysin L is a single-chain protein of about 25.5 kDa and pi 9.8. The enzyme is synthesized as a preproenzyme and the mature enzyme consists of 200 amino acids. Choriolysin L is colocalized with choriolysin H in the secretory granules of the hatching gland cells that are located in the inner wall of the pharyngeal cavity of prehatching medaka embryos.