Abstract
Judging from the results of previous reports, it is possible supposed that the inactivation of α-amylase by riboflavin in the light is due to the denaturation of enzyme protein. In order to ascertain this supposition, the characteristic changes of optical density, specific rotation and color reaction of enzyme protein are determined before and after the illumination in this paper. The inactivated enzyme protein shows not only remarkable increases of its optical density at 280 mμ and specific rotation but also marked changes in its specific color reactions which are peculiar to the aromatic amino acids, such as tyrosine and tryptophan. From these results it is deduced that the inactivation of α-amylase by riboflavin the light is attributable to the denaturation of enzyme protein, depending upon the irreversible changes of aromatic amino acids.
