The Physicochemical Characterization of Native and Denatured Carboxypeptidase A*

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Abstract
Trifluoro-acetate (0.28%), guanidine (3 [image]) and 1.10-phenanthroline (2x10-4 [image]) exert approximately parallel effects of inactivation and denaturation which is determined by the decrease in optical rotatory dispersion. Surface active agents of cationic (dodecyltrimethylammonium chloride), anionic (sodium dodecylsulfate) and non-ionic natures (Brij 35) show stronger inactivating effect than denaturing action. Brij 35 in the presence of NaCl (1 [image]) shows denaturing effect alone, but the Brij 35-NaCl mixture does not inactivate the enzyme, whereas beta-phenyl-propionic acid inhibits the enzyme without any denaturation. The enzyme possesses a high helix content (80%) when determined in 1.8 [image] NaCl; and the denatured, unfolded enzyme molecule takes the beta-form, the -NH- groups of which are readily exchangeable with deuterium of D2O. The above denaturing agents presumably unfold the enzyme protein in different ways.