Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: KEGG:D02011 (FAD)
 5,530 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A unique flavin-containing chloroperoxidase from the marine worm Notomastus lobatus was purified to homogeneity. This enzyme is composed of two dissociable protein moieties, a flavoprotein and a heme protein, in 1:1 molar ratio. The flavoprotein (Mr = 120,000) consists of four identical subunits having Mr of 30,000, and contains FAD. The heme protein (Mr = 54,000) is composed of two copies each of two non-identical subunits (Mr = 15, 500 and 11, 500) and contains ferriheme. The native N. lobatus chloroperoxidase (Mr = 174,000) therefore has a structure of alpha 4 beta 2 gamma 2. Neither the flavoprotein nor the heme protein alone has detectable chloroperoxidase activity but readily associate to form fully active enzyme. This enzyme is capable of oxidizing Cl-, Br-, and I- with optimum pH values of 4.5, 5.0, and 4.5, respectively, at 440 microM H2O2 and has halide-independent catalase activity in the absence of organic substrate. The enzyme can halogenate a wide variety of aromatic compounds, including phenol, from which it produces 4-bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol. The same compounds are found in N. lobatus. The N. lobatus chloroperoxidase is the first haloperoxidase to be purified to homogeneity from a marine polychaete, the first reported to contain flavin, and has several unusual physical and catalytic properties. This chloroperoxidase appears to represent a new class of haloperoxidases.
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PMID:Purification and properties of a unique flavin-containing chloroperoxidase from the capitellid polychaete Notomastus lobatus. 174 63

The alpha(2)beta(2) flavocytochrome p-cresol methylhydroxylase (PCMH) from Pseudomonas putida is composed of a flavoprotein homodimer (alpha(2) or PchF(2); M(r) = 119 kDa) with a cytochrome monomer (beta, PchC; M(r) = 9.3 kDa) bound to each PchF subunit. Escherichia coli BL21(DE3) has been transformed with a vector for expression of the pchF gene, and PchF is overproduced by this strain as the homodimer. During purification, it was recognized that some PchF had FAD bound, while the remainder was FAD-free. However, unlike PchF obtained from PCMH purified from P. putida, FAD was bound noncovalently. The FAD was conveniently removed from purified E. coli-expressed PchF by hydroxyapatite chromatography. Fluorescence quenching titration indicated that the affinity of apo-PchF for FAD was sufficiently high to prevent the determination of the dissociation constant. It was found that p-cresol was virtually incapable of reducing PchF with noncovalently bound FAD (PchF(NC)), whereas 4-hydroxybenzyl alcohol, the intermediate product of p-cresol oxidation by PCMH, reduced PchF(NC) fairly quickly. In contrast, p-cresol rapidly reduced PchF with covalently bound FAD (PchF(C)), but, unlike intact PCMH, which consumed 4 electron equiv/mol when titrated with p-cresol (2 electrons from p-cresol and 2 from 4-hydroxybenzyl alcohol), PchF(C) accepted only 2 electron equiv/mol. This is explained by extremely slow release of 4-hydroxybenzyl alcohol from reduced PchF(C). 4-Hydroxybenzyl alcohol rapidly reduced PchF(C), producing 4-hydroxybenzaldehyde. It was demonstrated that p-cresol has a charge-transfer interaction with FAD when bound to oxidized PchF(NC), whereas 4-bromophenol (a substrate analogue) and 4-hydroxybenzaldehyde have charge-transfer interactions with FAD when bound to either PchF(C) or PchF(NC). This is the first example of a "wild-type" flavoprotein, which normally has covalently bound flavin, to bind flavin noncovalently in a stable, redox-active manner.
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PMID:Properties of p-cresol methylhydroxylase flavoprotein overproduced by Escherichia coli. 1060 Jan 24