Abstract
As reported previously, two decomposition products of FAD, namely Y_1 and Y_2,were detected. Further experiments were performed on some properties of Y_1. The results were as follows : Effect of pH on fluorescence of a solution of the substance and its absorption spectrum were similar to those of FMN. Under an acid hydrolysis of Y_1,FMN was produced and then the fluorescence of solution decreased in some degree. Analysis of Y_1 indicated that the substance contained two moles of phosphate per a flavin moiety. The above results support a supposition that Y_1 may be P^1-(riboflavin-4', 5'-cyclic)-pyrophosphate produced by separation of adenosine moiety from FAD-X.
