Miceli D C, Fernandez S N
J Exp Zool. 1982 Jul 1;221(3):357-64. doi: 10.1002/jez.1402210311.
The secretion produced at the most cephalic portion of the oviduct of the toad (pars recta in Bufo arenarum) is involved in fertilization. Although the present study indicates that a prerequisite for the fertilization of coelomic eggs is either their passage through the pars recta (PR) or their treatment with PR secretion fluid prior to insemination, the exact role of this secretion in the fertilization process is still not clearly understood. A protein acting upon the vitelline envelope (VE) of Bufo arenarum coelomic eggs has been purified from secretion fluid (pars recta protein, PRP). Some properties of both this protein and the secretion fluid are examined in an effort to understand their mechanism of action. It was shown that PRP partially dissolves the VE of coelomic oocytes in a way that resembles the action of proteolytic enzymes. PRP has also proved to be active on synthetic substrates of proteolytic enzymes such as p-Tosyl-L-arginine methyl ester-HCl (TAME), alpha-N-benzoyl-L-arginine ethyl ester-HCl (BAEE), and alpha-N-benzoyl-DL-arginine-p-nitroanilide HCl (BAPNA). PR enzyme is activated by calcium ions, shows a broad peak of maximum activity at pH 7.8, is stable at alkaline pH, and is inhibited by soybean trypsin inhibitor (SBTI) and N-alpha-p-tosyl-L-lysine chloromethyl ketone HCl (TLCK) but not by lima bean trypsin inhibitor (LBTI) or L-1-tosyl-amide-2-phenylethylchloro-methyl-ketone (TPCK).
蟾蜍输卵管最头部区域（南美蟾蜍的直肠部）产生的分泌物参与受精过程。尽管本研究表明，体腔卵受精的一个先决条件是它们要么通过直肠部（PR），要么在授精前用PR分泌液处理，但这种分泌物在受精过程中的确切作用仍不清楚。一种作用于南美蟾蜍体腔卵卵黄膜（VE）的蛋白质已从分泌液中纯化出来（直肠部蛋白质，PRP）。为了解它们的作用机制，对这种蛋白质和分泌液的一些特性进行了研究。结果表明，PRP能部分溶解体腔卵母细胞的VE，其方式类似于蛋白水解酶的作用。PRP还被证明对蛋白水解酶的合成底物如对甲苯磺酰-L-精氨酸甲酯盐酸盐（TAME）、α-N-苯甲酰-L-精氨酸乙酯盐酸盐（BAEE）和α-N-苯甲酰-DL-精氨酸对硝基苯胺盐酸盐（BAPNA）有活性。PR酶被钙离子激活，在pH 7.8时显示出一个宽泛的最大活性峰，在碱性pH下稳定，并且被大豆胰蛋白酶抑制剂（SBTI）和N-α-对甲苯磺酰-L-赖氨酸氯甲基酮盐酸盐（TLCK）抑制，但不被利马豆胰蛋白酶抑制剂（LBTI）或L-1-对甲苯磺酰-酰胺-2-苯乙基氯甲基酮（TPCK）抑制。
