On the Enzymatic hydrolysis of FAD in spinach leaves.

The existence and biochemical functions of flavin adenine dinucleotide (FAD) have been well recognized in plants as well as in other living cells. There are some informa tions concerning the biosynthesis of FAD from flavin mononucleotide (FMN) and ATP by a reversible reaction, catalzyed by FAD pyrophosphorylase in beans (1), yeast (2, 3) and animals (4, 5, 6). On the other hand, the FAD hydrolysis by nucleotide pyrophosphatase (EC 3.6.1.9) has been demonstrated in potato (7), pigeon liver (8), tobacco root (9) and mung bean seedlings (10), but has not been reported in green leaves. Recently the present authors found that the disintegration of FAD to FMN was caused by the irreversible hydrolysis of FAD catalyzed by the nucleotide pyrophosphatase, and that the activity of this enzyme overbore that of the FAD synthesizing enzyme. Some basic properties of the enzyme on the hydrolysis of FAD in spinach leaves are dealt with in this paper.