3.2. N-terminal amino acid sequence of Z. ophiocephalus trypsin
The N-terminal 9 amino acids of the Z. ophiocephalus trysin were determined to be IVGGYECQP. The N-terminal amino acid sequence of Z. ophiocephalus trypsin showed uniformity, indicating that it was isolated in a pure form and, if other isoforms are present, their amounts must be small. The N-terminal amino acid sequence of Z. ophiocephalus trypsin was aligned with the sequences of other animal trypsins (Fig. 2). The alignment indicates that the first four NH2-terminal amino acid residues (IVGG) are conserved in all trypsins. The sequence of inhibitors. On the other hand, the metalloprotease inhibitor (EDTA,5 mM) inhibited the enzyme by 59%. The relatively high activity of the trypsin in the presence of EDTA is very useful for application as detergent additive because chelating agents are components of most detergents. Chelating agents function as water softeners and also assist in the removal of stain. These agents specifically chelate metal ions making them unavailable in the detergent solution. In addition, Pepstatin A, an aspartic protease inhibitor and DTNB, specific for thiol proteases, did not show any inhibitory effects against the purified trypsin. The inhibition results indicate that the purified enzyme is a serine-protease based on inhibition by PMSF and authentic trypsin based on its catalytic specificity for BAPNA and inhibition by SBTI.