Proteolysis of Wool and its S-Carboxymethyl Derivatives by Pronase and Other Proteases

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Abstract
The proteolysis of native Merino wool by pronase, a protease from Streptomyces griseus, was shown to resemble that of other proteases in liberating cortical cells and solubilizing less than 20% of the fibre. The action of proteases on fully reduced and alkylated wool and on soluble wool proteins was compared. Modified whole wool was digested most rapidly by pronase and the least readily by pepsin (3.4.4.1). High-sulphur proteins extracted from wool were broken down by pepsin initially at least 10 times faster than the low-sulphur proteins. The structural significance is discussed. An attempt was made to determine whether peptide bonds in the vicinity of the more readily reducible disulphide bonds were the most susceptible to proteolysis. Varying proportions of the carboxymethyl eroups of fully reduced and alkylated preparations were labelled with 14C. The release of trichloroacetic acid-soluble 14C and nitrogen was measured after varying periods of incubation with proteases. The rate of liberation of 14C from modified whole wool bv pronase and trypsin (3.4.4.4) was independent of the proportion of 14C present in the preparations. With pepsin, the 14C release was variable, but the ratio of percentage 14C release to percentage nitrogen release was constant and thus not related to the proportion of labelled-S-carboxymethyl groups present. The rate of production of 14C soluble in trichloroacetic acid from the high-sulphur proteins was also independent of the proportion of 14C label present. The more easily reducible portion of the low-sulphur proteins appeared to be somewhat more resistant to proteolysis than the rest of the molecule, but when the nitrogen liberation was taken into account, a lack of dependence on the 14C content could once again be demonstrated. These and other findings are consistent with a random distribution of the more easily reducible disulphide bonds in the wool fibre.