STEREO-SPECIFIC INHIBITION OF SEA-URCHIN ENVELYSIN (HATCHING ENZYME) BY A SYNTHETIC AUTOINHIBITOR PEPTIDE WITH A CYSTEINE-SWITCH CONSENSUS SEQUENCE

Inhibition of envelysin, a metalloproteinase which dissolves the fertilization envelope of sea urchin embryo, was studied using a synthetic autoinhibitor peptide, Ac-Pro-Arg-Cys-Gly-Val-Pro-Asp-Val-NH2, with a 'cysteine-switch' consensus sequence. Although its effect is reversible, the hatching of sea urchin embryos was effectively delayed by 0.5 mM of the peptide. When alpha1-proteinase inhibitor was used as the substrate, envelysin was inhibited by the autoinhibitor and an Ala6 analogue, but not by a D-Cys3 analogue. However, envelysin was weakly inhibited by both D- and L-Cysteines to the same extent. Snake venom alpha-protease exhibited cleavage and inhibition behavior similar to envelysin with a little weaker stereo-specificity. The results suggest that the coordination of the autoinhibitor Cys residue with the envelysin active site Zn is established only after the amino acid residues on both sides of the Cys residue get into an appropriate interaction with the catalytic site residues, and that the precise orientation of the cysteine SH group is essential. By contrast, thermolysin was weakly inhibited by the three peptide non-stereo-specifically. Furthermore, thermolysin cleaved the autoinhibitor at the Cys3-Gly4 bond when incubated without substrate.