Inhibition of Mouse Blastocyst Hatching by Subsite-Specific Trypsin Inhibitors, Peptidyl Argininals

To explore the substrate or subsite specificity of a mouse hatching enzyme, effects of leupeptin [acetyl(P4 )-Leu(P3 )-Leu(P2 )-argininal(P1 )] and its analogs (peptidyl argininals) on mouse blastocyst hatching were investigated. The compounds containing benzyloxycarbonyl group (Z) in the P4 position inhibited the hatching more strongly than those containing acetyl group or unprotected N-terminal amino acid. Among five Z-Leu-P2 -argininals, a derivative containing a P2 Ser residue was the most potent inhibitor, and the derivatives containing Leu, Thr, Pro, and Gly in the P2 position followed in this order. Then, we synthesized four Z-P3 -Ser-argininals and tested their effects on hatching. The result indicated that the compound with Phe residue in the P3 position was the strongest inhibitor, and the Leu-, Pro-, and Ala-containing derivatives were ranked in this order. Thus, among Z-dipeptidyl-argininals tested, Z-Phe-Ser-argininal most potently inhibited the mouse embryonic hatching, suggesting the preference of the mouse hatching enzyme for Phe(P3 )-Ser(P2 )-Arg(P1 ) sequence as a substrate.