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

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.