On the esterolytic activities of papain and trypsin.

The ability of papain to split esters of the type hydrolyzed by trypsin has been reported from this laboratory (1) and has also been independently observed by other workers (2) at about the same time. The esters studied here were the methyl esters of cY-N-benzoylarginine and its nitro derivatives. It was observed that the presence of a nitro group on the benzene ring of the ester altered considerably the sensitivity of the substance to both papain and trypsin. The extent and, in the case of trypsin, the direction of this change depended upon the position of the nitro group on the ring. The presence of a nitro group in the ortho position was found to accelerate the hydrolysis of the ester with either enzyme. When the group occupied the meta or para position, the action of papain was still accelerated, though to a lesser degree, while the action of trypsin was retarded. The latter, however, returned to the level observed with the unnitrated substrate on the introduction of a second nitro group. In the case of papain, the position of the nitro group has considerable influence on the rate of complex formation between enzyme and substrate, and the results with the mononitro compounds can be explained on this basis.