A correlation observed between loss of tryptophan and loss of reactivity to N-benzoyl tyrosine ethyl ester following irradiation of dilute solutions of chymotrypsin in both air (2) and nitrogen atmospheres is not general for all synthetic substrates. The loss of activity by the enzyme on irradiation with x- and γ-rays has been measured using nine synthetic substrates including both esters and amides. It was found that the$D_{37}$ observed was a function of the substrate employed, and parallel results were obtained from irradiations in air and in nitrogen. Oxygen was protective. The data found for the range of substrates confirmed the results from Lineweaver-Burk plots obtained with esters of tyrosine: both acylation and deacylation processes of chymotrypsin were affected by irradiation.

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