The Contribution of the Single Tryptophyl Residues to the Fluorescence Emission of Porcine Elastase

Abstract

In order to evaluate the contribution of the single tryptophyl residues to the fluorescence emission of elastase, the latter was analyzed as a function of pH, as well as in the presence of some perturbants and quenchers. Moreover, specific tryptophyl residues were converted to formyl-kynurenine by photosensitized oxidation. Our results suggest that the two external tryptophans 26 and 164 account for at least 50% of the total emission; out of the two partially buried tryptophans, the residue 83 is practically non-fluorescent, whereas the residue 12 contributes about one fourth of the elastase fluorescence. The residual fluorescence (about 25% of the total emission) is to be ascribed to the three deeply buried tryptophans 39, 132 and 232.