Isolation and purification of three egg-membrane lysins from sperm of the marine invertebrate Megathura crenulata (giant keyhole limpet)

Two major acrosomal proteins act on different parts of the oocyte vitelline coat in the abalone, Haliotis discus

Two proteins of molecular weights 20,000 (20K) and 15,500 (15.5K) are the major soluble substances released from the acrosomal vesicle of the abalone, Haliotis discus, spermatozoon. A crude preparation of them has been shown to possess lytic activity on the oocyte vitelline coat (VC). To elucidate the role(s) of each acrosomal protein (AP) in VC lysis, oocytes were examined after treatment with various AP preparations. The VC, which is about 1 micron thick, is composed of thin outer and inner electron-dense layers and a thick main layer of a fine filamentous feltwork. When oocytes were treated with a crude preparation containing both APs, the outer layer disappeared and the feltwork of the main layer loosened extensively. A preparation containing predominantly the 20K AP dissolved the outer layer completely and the main layer to some extent, whereas another preparation containing predominantly the 15.5K AP caused loosening of the main layer without alteration of the outer layer, suggesting that the 20K AP acts on the outer layer, whereas the 15.5K AP acts on the main layer. However, when purified, each AP by itself failed to dissolve the VC, although lysis occurred in a 1:1 mixture of these preparations. Moreover, when the oocytes were pretreated with the 20K AP and thoroughly washed, the 15.5K AP alone could induce lysis. These results suggest that the lysis of the outer layer requires both APs but not simultaneously. The 15.5K AP, which is located posteriorly in the acrosomal vesicle, must be released to act on the VC following the action of the 20K AP.

Purification and characterization of a chymotrypsin-like enzyme from sperm of the sea urchin, Hemicentrotus pulcherrimus

A chymotrypsin-like enzyme has been purified from sperm of the sea urchin, Hemicentrotus pulcherrimus, using tryptophan methyl ester (TrpOMe) linked to Sepharose 4B as an affinity column for chromatography and gel filtration. The isolated enzyme preparation is homogeneous in sodium dodecylsulfate/polyacrylamide gel electrophoresis, the estimated molecular weight being 18,500-19,000. This enzyme hydrolyses N-acetyl-L-tyrosine ethyl ester (AcTyrOEt) and N-benzoyl-L-tyrosine ethyl ester (BzTyrOEt); the optimal pH is 8.0. It does not hydrolyse N-benzoyl-L-arginine ethyl ester, N-alpha-toluenesulfonyl-L-arginine methyl ester, N-alpha-benzoyl-DL-arginine-p-nitroanilide, hippuryl-L-arginine or hippuryl-L-phenylalanine. The Michaelis constants for AcTyrOEt and BzTyrOEt are 0.05 mM and 0.0106 mM, respectively. The enzyme activity is inhibited completely by phenylmethylsulfonyl fluoride (PhMeSO2F), chymostatin and L-1-tosylamido-2-phenylethyl chloromethyl ketone (TosPheCH2Cl), and partially by soybean trypsin inhibitor and N-alpha-p-tosyl-L-lysine chloromethyl ketone (TosLysCH2Cl). The enzyme is activated by CaCl2, MgCl2, NaCl and KCl, and loses its activity in 5 min at 67 degrees C. It digests the jelly coat and vitelline layer, not the fertilization membrane. The microvilli of unfertilized eggs elongate and decrease in number as the vitelline layer lyses. The vitelline layer lytic activity is inhibited completely by PhMeSO2F, TosPheCH2Cl, and chymostatin, and partially by soybean trypsin inhibitor, TosLysCH2Cl, and alpha 1-antitrypsin. We have confirmed by transmission electron microscopy that our chymotrypsin-like enzyme completely digests the vitelline layer. A result implying release of this enzyme from the acrosome vesicle is also reported.

Ultrastructural demonstration of trypsin-like protease in acrosomes of sea urchin sperm

Two independent cytochemical techniques were used to demonstrate that a trypsin-like protease is bound to the acrosomal tubule of the sea urchin sperm. The enzyme is associated with binding on the reacted acrosome and presumably functions in the early phases of fertilization.