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FUNCTION This enzyme has two activities: FAD diphosphatase activity and FAD synthase activity (PubMed:16643857, PubMed:21924249, PubMed:21951714, PubMed:23443125, PubMed:25135855, PubMed:26277395, PubMed:27259049, PubMed:31351152, PubMed:38688286). FAD diphosphatase acts on FAD and NADH to produce FMN and NMNH(2-), respectively (PubMed:26277395, PubMed:31351152, PubMed:38688286). FAD synthase catalyzes the adenylation of flavin mononucleotide (FMN) to form flavin adenine dinucleotide (FAD) coenzyme (PubMed:16643857, PubMed:21924249, PubMed:21951714, PubMed:23443125, PubMed:27259049, PubMed:38688286). In addition to its catalytic activities, the protein also facilitates the delivery of FAD to client apo-flavoproteins (PubMed:25954742). The balance between FAD synthesis and hydrolysis may be regulated by redox-sensing cysteine residues (PubMed:25135855, PubMed:26277395). At a much lower rate, FAD synthase catalyzes the reverse pyrophosphorolytic reaction (PubMed:21951714, PubMed:23443125, PubMed:25135855, PubMed:26277395). FAD synthase can also convert roseoflavin mononucleotide (RoFMN) to roseoflavin adenine dinucleotide (RoFAD); RoFMN is produced by riboflavin kinase when acting on the antibiotic roseoflavin (RoF) (PubMed:21924249). FAD synthase cannot convert 8-demethyl-8-amino-riboflavin mononucleotide (AFMN) to 8-demethyl-8-amino-riboflavin adenine dinucleotide (AFAD); AFMN is produced by riboflavin kinase when acting on the antibiotic 8-demethyl-8-amino-riboflavin (AF) (PubMed:21924249).CATALYTIC ACTIVITY FAD + H2O = FMN + AMP + 2 H(+)CATALYTIC ACTIVITY NADH + H2O = reduced beta-nicotinamide D-ribonucleotide + AMP + 2 H(+)CATALYTIC ACTIVITY FMN + ATP + H(+) = FAD + diphosphateCOFACTOR The FAD synthase activity requires a divalent metal (PubMed:16643857, PubMed:17049878, PubMed:21951714, PubMed:23443125). Magnesium or cobalt supports the highest FAD synthase activity, it has lower activity with manganese, calcium or zinc (PubMed:21951714, PubMed:23443125). Magnesium is also required for the reverse pyrophosphorolytic reaction (PubMed:21951714, PubMed:23443125, PubMed:26277395). Cobalt does not appear to support the reverse reaction (PubMed:26277395).COFACTOR The FAD diphosphatase activity requires cobalt (PubMed:26277395, PubMed:31351152). Nickel and manganese can substitute with much lower efficiency (PubMed:31351152). Magnesium, calcium and copper cannot substitute (PubMed:26277395, PubMed:31351152).COFACTOR The FAD diphosphatase activity requires potassium (PubMed:31351152). Can also use sodium to a lesser extent (PubMed:31351152).ACTIVITY REGULATION The reducing agent sodium dithionite stimulates FAD synthase activity (PubMed:21924249). The FAD synthase activity is inhibited by GTP and GDP (PubMed:21951714, PubMed:23443125). The FAD synthase activity is also inhibited by the thiol reagents mersalyl, methylmercury, and mercury chloride; mersalyl also inhibits the reverse pyrophosphorylase activity (PubMed:25135855). FAD diphosphatase activity is stimulated by glutathione and mersalyl (PubMed:26277395, PubMed:31351152). FAD diphosphatase activity is inhibited by ADP and ADP-ribose (PubMed:26277395, PubMed:31351152).BIOPHYSICOCHEMICAL PROPERTIES kcat is 0.69 sec(-1) for FAD synthase activity using enzyme purified from E.coli (at 37 degrees Celsius and at pH 7.5) (PubMed:21951714). kcat is 0.69 sec(-1) for FAD synthase activity using enzyme purified from E.coli (at 37 degrees Celsius and at pH 7.5) (PubMed:25135855). kcat is 0.02 sec(-1) for FAD synthase activity using enzyme purified from P.pastoris (at 37 degrees Celsius and at pH 7.5) (PubMed:21924249). kcat is 0.08 sec(-1) for FAD synthase activity in presence of sodium dithionite using enzyme purified from P.pastoris (at 37 degrees Celsius and at pH 7.5) (PubMed:21924249). kcat is 0.07 sec(-1) with roseoflavin adenine dinucleotide as substrate and in presence of sodium dithionite using enzyme purified from P.pastoris (at 37 degrees Celsius and at pH 7.5) (PubMed:21924249). kcat is 0.116 sec(-1) for FAD diphosphatase activity using enzyme purified from E.coli (at 37 degrees Celsius and at pH 7.5) (PubMed:31351152). kcat is 0.0069 sec(-1) for the reverse pyrophosphorolytic reaction using enzyme purified from E.coli (at 37 degrees Celsius and at pH 7.5) (PubMed:25135855).BIOPHYSICOCHEMICAL PROPERTIES kcat is 0.042 sec(-1) for FAD synthase activity using C-terminal region (329-587) purified from E.coli (at 37 degrees Celsius and at pH 7.5) (PubMed:23443125). kcat is 0.0037 sec(-1) for the reverse pyrophosphorolytic reaction using C-terminal region (329-587) purified from E.coli (at 37 degrees Celsius and at pH 7.5) (PubMed:23443125).PATHWAY Cofactor biosynthesis; FAD biosynthesis; FAD from FMN: step 1/1.SUBUNIT Dimer (PubMed:38688286). Interacts with KDM1A; which promotes KDM1A holoenzyme formation (PubMed:25954742). Interacts with DMGDH; which promotes DMGDH holoenzyme formation (PubMed:25954742).INTERACTION May form disulfide bonds.DISEASE The disease is caused by variants affecting the gene represented in this entry.SIMILARITY In the N-terminal section; belongs to the MoaB/Mog family.SIMILARITY In the C-terminal section; belongs to the PAPS reductase family. FAD1 subfamily.
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