LYTIC ENZYMES OF SORANGIUM SP.: A COMPARISON OF SOME PHYSICAL PROPERTIES OF THE α- AND β-LYTIC PROTEASES

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Abstract
Ultraviolet absorption spectra of the two enzymes were determined. The β-enzyme has the lower λmax and the higher absorptivity between 260 and 300 mμ. The spectra in 0.1 N alkali – 8 M urea indicated that the β-enzyme has a substantially higher ratio of tyrosine to tryptophan residues and a substantially higher content of both amino acids.Electrophoresis in starch gel at pH 8 and in cellulose acetate at pH's from 3 to 9 showed no evidence of heterogeneity in the enzyme preparations, but the electrophoretic pattern of the β-enzyme in acetate – 7 M urea buffer depends on the period of preexposure of enzyme to the buffer; brief or prolonged (24 hours) periods give patterns with one component, intermediate periods can give patterns with two components. In all buffers tested, the mobility of the α-enzyme was slightly greater than that of lysozyme; in all buffers except those containing phosphate, the mobility of the β-enzyme was slightly less than that of lysozyme.The molecular weight of both enzymes was estimated to be 19,000 by the Archibald method; the estimate for the β-enzyme assumes a partial specific volume of 0.72. The elution volume/void volume ratios of the enzymes were compared in Sephadex G75. The ratio for the α-enzyme was consistent with a molecular weight of approximately 19,000. The ratio for the β-enzyme was anomalously high; the enzyme is probably weakly adsorbed on the gel. Neither enzyme showed any indication of heterogeneity on displacement from hydroxylapatite.