Purification of Co‐ARIS, a Cofactor for Acrosome Reaction‐Inducing Substance, from the Egg Jelly of Starfish

Abstract
In the starfish, Asterias amurensis, the acrosome reaction-inducing capacity of the egg jelly has been attributed to two components in the egg jelly: a sulfated glycoprotein (ARIS) and an unidentified low-molecular weight substance (Co-ARIS). In the process of purification of Co-ARIS, we found that Co-ARIS is not a single chemical entity but a series of closely related molecules. Co-ARIS was first group-separated by using octadecylsilane and anion-exchanger. Three major Co-ARIS'' (I, II and III) were then purified by successive chromatographies using octadecylsilane and silica gel to the homogeneity in thin layer chromatography. Each of purified Co-ARIS'', together with ARIS or the Pronase-digest of ARIS, induced the acrosome reaction at high ratios in normal seawater.