Description:
<jats:title>Abstract</jats:title><jats:p>The chorionase (hatching enzyme) of <jats:italic>Fundulus heteroclitus</jats:italic> digests the chorion by producing water soluble peptide fragments. The chorion may be labeled with <jats:sup>14</jats:sup>C‐iodoacetamide so that the soluble products of digestion are also labeled. We used this labeled substrate as the basis for a quantitative assay for chorionase. Chorionase was found to be quite stable at temperatures below 30°C and had a Q<jats:sub>10</jats:sub> of 2.2 between 15 and 30°C. The pH optimum for enzymatic activity was between pH 8.0 and pH 8.5, and an ionic strength optimum was found between 0.1M and 0.2M. The enzyme was inhibited at ionic strengths similar to those found in sea water. Chorionase was also inhibited by divalent cations, EDTA, and PMSF. These results suggest that divalent cations are necessary for activity even though they are inhibitory at concentrations above 10mM.</jats:p>