Abstract Chymotrypsin was isolated from ovine and porcine pancreas by affinity chromatography on immobilised 4‐phenylbutylamine. The apparent molecular weights of the two proteins were estimated by SDS PAGE to be 25.7 and 27.3 kD respectively. Specific activities for ovine and porcine chymotrypsins (OC and PC) were 32.8 and 31.2 μmol/min per mg, respectively, at pH 8.5 and 25°C using 0.1 mM N‐succinyl‐Ala‐Ala‐Pro‐Phe‐pNA (SAAPFpNA) as substrate. Values of the Michaelis constants for ovine and porcine chymotrypsins with SAAPFpNA were comparable at pH 8.0 and at temperatures between 20 and 45°C, as were the kcat values. Both enzymes were stable under acidic conditions but were susceptible to thermal denaturation above 45°C. Hydrolysis of lysozyme and casein by ovine or porcine chymotrypsin yielded very similar fragmentation profiles as determined by RP‐HPLC.
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