Isolation and characterization of a trypsin fraction from the pyloric ceca of chinook salmon (Oncorhynchus tshawytscha).

A trypsin fraction was isolated from the pyloric ceca of New Zealand farmed chinook salmon (Oncorhynchus tshawytscha) by ammonium sulfate fractionation, acetone precipitation and affinity chromatography. The chinook salmon enzyme hydrolyzed the trypsin-specific synthetic substrate benzoyl-DL-arginine-p-nitroanilide (DL-BAPNA), and was inhibited by the general serine protease inhibitor phenyl methyl sulfonyl fluoride (PMSF), and also by the specific trypsin inhibitors - soybean trypsin inhibitor (SBTI) and benzamidine. The enzyme was active over a broad pH range (from 7.5 to at least pH 10.0) at 25 degrees C and was stable from pH 4.0 to pH 10.0 when incubated at 20 degrees C, with a maximum at pH 8.0. The optimum temperature for the hydrolysis of DL-BAPNA by the chinook salmon enzyme was 60 degrees C, however, the enzyme was unstable at temperatures above 40 degrees C. The molecular mass of the chinook salmon trypsin was estimated as 28 kDa by SDS-PAGE.