Flavin adenine dinucleotide pyrophosphorylase

A specific kinase, flavokinase, yields flavin mononucleotide in the presence of riboflavin and ATP, and probably magnesium. Schrecker and Kornberg [97] described an enzyme that catalyzes the synthesis of flavin adenine dinucleotide from flavin mononucleotide and ATP. The enzyme was isolated from yeast, and similar enzymes have been found in animal tissues. The enzyme is called flavin adenine dinucleotide pyrophosphorylase. 

It was not certain from the above observations whether the synthetis of flavin adenine dinucleotide in animal tissues proceeded by the same mechanism as that demonstrated with the purified enzyme from yeast. The demonstration by Watarai et al. 140) that flavin adenine dinucleotide synthesized from riboflavin 5 -phosphate-P and ATP in rabbit liver homogenates had the same molar specific radioactivity as added riboflavin 5 -phosphate-P would be in accord with a flavin adenine dinucleotide-pyrophosphorylase reaction, but suffered from the lack of demonstration of net synthesis of the coenzyme in the system. 

In higher mammals, riboflavin is absorbed readily from the intestines and distributed to all tis.sues. It is the precursor in the biosynthesis of the cocnzyme.s flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). The metabolic functions of this vitamin involve these Iwocoenzymes. which participate in numerous vital oxidation-reduction proces.ses. FMN (riboflavin 5 -phosphate) is produced from the vitamin and ATP by flavokinasc catalysis. This step con be inhibited by phcnothiazincs and the tricyclic antidepressants. FAD originates from an FMN and ATP reaction that involves reversible dinucicotide formation catalyzed by flavin nucleotide pyrophosphorylase. The.se coenzymes function in combination with several enzymes as coenzyme-en-zyme complexes, often characterized as, flavoproteins. 

Flavin Coenzymes.—5-Deazaflavin-adenine dinucleotide (2) can be prepared from the 5-deazaFMN,21 using a FAD pyrophosphorylase from rat liver.22 When the apoprotein of D-amino-acid oxidase from pig kidney is reconstituted with (2), no oxidation of D-alanine is observed, although the flavin chromophore in the reconstituted enzyme is reduced on the addition of DL-amino-acids.22 This has been interpreted as indicating that hydrogen transfer from the amino-acid to (2) can still... 

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See also in sourсe #XX -- [ ]

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