Effect of Adenine on the Riboflavin-sensitized Photoreaction:I. Effect of Adenine on the Photodynamic Inactivation of Yeast Alcohol Dehydrogenase in the Presence of Riboflavin

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Upon the addition of adenine, the remarkable enhancement of the riboflavinsensitized photoinactivation of yeastalcohol dehydrogenase [EC 1.1.1.1] was observed, and the inactivation of the enzyme was found to be a first-order reaction. The extent of the enhancement calculated from the apparent rate constants was about five times. An attempt to analyse the action spectra revealed that quantum efficiency increased approximately three times. Adenine had no effect on the photodynamic inactivation of the enzyme in the case where methylene blue, eosin yellowish or fluorescein was used as a sensitizer in place of riboflavin. The ability of adenine to enhance the inactivation was exhibited only when flavin, such as riboflavin, FMN or FAD, was employed as a sensitizer. The accelerative effect similar to that of adenine was also observed with several purine derivatives such as guanine. Of the amino acids susceptible to the riboflavin-sensitized photooxidation, only cysteine was photooxidized increasingly by the addition of adenine.The mechanism through which adenine causes the enhancement of the riboflavin-sensitized photoinactivation of the enzyme is discussed in correlation with the ability of adenine to form a molecular complex with riboflavin.
日本ビタミン学会の論文