title: Antioxidative galloyl esters as enzyme inhibitors of p-hydroxybenzoate hydroxylase.
abstract: Gallic acid and its esters were evaluated as enzyme inhibitors of recombinant p-hydroxybenzoate hydroxylase (PHBH), a NADPH-dependent flavin monooxygenase from Pseudomonas aeruginosa. n-Dodecyl gallate (DG) (IC(50)=16 microM) and (-)-epigallocatechin-3-O-gallate (EGCG) (IC(50)=16 microM), a major component of green tea polyphenols, showed the most potent inhibition, while product-like gallic acid did not inhibit the enzyme significantly (IC(50)>250 microM). Inhibition kinetics revealed that both DG and EGCG inhibited PHBH in a non-competitive manner (K(I)=18.1 and 14.0 microM, respectively). The enzyme inhibition was caused by specific binding of the antioxidative gallate to the enzyme, and by scavenging reactive oxygen species required for the monooxygenase reaction. Molecular modeling predicted that EGCG binds to the enzyme in the proximity of the FAD binding site via formation of three hydrogen bonds.
authors.affiliation: School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan. abei@ys7.u-shizuoka-ken.ac.jp
authors.forename: I
authors.initials: I
authors.lastname: Abe
authors.forename: K
authors.initials: K
authors.lastname: Kashiwagi
authors.forename: H
authors.initials: H
authors.lastname: Noguchi
mesh_terms: D015109:4-Hydroxybenzoate-3-Monooxygenase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D000975:Antioxidants / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004952:Esters; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D007700:Kinetics; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010226:Parabens / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000201:enzymology / Q000235:genetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D000975:Antioxidants; D004791:Enzyme Inhibitors; D004952:Esters; D010226:Parabens; D011994:Recombinant Proteins; C008259:lauryl gallate; D005707:Gallic Acid; D002392:Catechin; C045651:epigallocatechin gallate; D015109:4-Hydroxybenzoate-3-Monooxygenase; C038193:4-hydroxybenzoic acid