An alkaline trypsin was purified from the viscera of zebra blenny (Salaria basilisca) by ammonium sulphate
(4080% saturation) precipitation, Sephadex G-100, Mono Q-Sepharose and ultrafiltration. A yield of 12% with a purification-fold of 4.2 was obtained. The trypsin had an apparent molecular weight of 27 kDa. Soybean trypsin inhibitor and phenylmethylsulfonyl fluoride showed a strong inhibitory effect on the purified trypsin. Trypsin had maximal activity at pH 9.5 and 60 C for the hydrolysis of Na-benzoyl-DL-arginine-pnitroanilide (BAPNA). It was stable at low temperatures and in the pH range of 7.012.0. The N-terminal amino acid sequence of the first 12 amino acids of the purified protease wasIVGGRECTEPSQ. S. basilisca trypsin, which showed high homology with other fish trypsins, had a charged Arg residue at position 5, where Tyr iscommon in marine vertebrates and mammalian trypsins. The trypsin kinetic constants, Kmand kcat for BAPNA, were 0.6 mM and 1.38 s1, respectively.