Studies on the soluble products released from purified elastic fibers by pancreatic elastase.

Abstract The release of substances from purified elastin by the action of pancreatic elastase was examined in relation to protein solubilization. There is a progressive increase in the amount of soluble protein produced per unit enzyme upon repeated exposures of the fibrous substrate to elastase. Early in protcolysis approximately 50% of the total solubilized protein is precipitated by trichloroacetic acid (TCA). The proportion of TCA-insoluble protein progressively increases so that, when solubilization is essentially complete, this fraction comprises 80% of the total. In contrast to the TCA-soluble protein, the TCA-insoluble component is associated with the yellow pigment observed in native elastin, is Schiff-positive, and is degraded by elastase. Elastase cleaves peptides or amino acids from the TCA-insoluble protein rendering it TCA-soluble; fluorescence, yellow pigmentation, and Schiff-positive material remain nondialyzable throughout. Both protein fractions exhibit identical fluorescence maxima at 340, 405, 440, and 460 mμ, but the ratio of fluorescence to protein in the case of the TCA-insoluble protein is twice that of the other. The component fluorescing at 340 mμ appears to be localized to the outer aspect of the elastic fiber, while the other fluorescent substances apparently are distributed throughout. It is suggested that TCA-soluble and TCA-insoluble proteins released during enzymic hydrolysis correspond to the amorphous matrix and fibrous components of the elastic fiber, respectively, seen microscopically. That the fluorescent components may be concerned with cross-linking in elastin is discussed.