Riboflavin-Sensitized Photoinactivation of Taka-Amylase A

Abstract

Taka-amylase A is strongly inactivated by the irradiation of visible light in the presence of riboflavin. The inactivation of amylase is ascribed to the photoöxidation of amino acid residues. The complete inactivation was obtained at the oxidation of about 70% tryptophan, 45% histidine, 20% tyrosine, 4% methionine and 17% cystine residues. The photooxidation of amino acids is affected by the state of their existence; whether they are free or bound to form a high polymer. In this connection, the effects of denaturation and formation of enzyme-substrate complex on photoöxidation of amino acid residues were discussed. Furthermore, the inhibition of photo-inactivation and -öxidation, and the quenching of fluorescence and phosphorescence of riboflavin were investigated in the presence of paramagnetic ions. The results obtained show that the triplet state of riboflavin seems to be essential for the process of riboflavin sensitized photoinactivation of taka-amylase A. © 1966, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.