title: Fatty acid signals in Bacillus megaterium are attenuated by cytochrome P-450-mediated hydroxylation.
abstract: In previous publications [English, Hughes and Wolf (1994) J. Biol. Chem. 269, 26836-26841; English, Hughes and Wolf (1996) Biochem. J. 316, 279-283], we have demonstrated that peroxisome proliferators and non-steroidal anti-inflammatory drugs are inducers of the cytochrome P-450BM-3 gene in Bacillus megaterium ATCC14581. Their mechanism of action involves binding to and subsequent displacement of the transcriptional repressor, Bm3R1, from its operator site, which results in the activation of cytochrome P-450BM-3 gene transcription. We now present evidence that the branched-chain fatty acid, phytanic acid, is a potent inducer of cytochrome P-450BM-3. We have also observed that phytanic acid and peroxisome proliferators are inducers of Bm3R1 protein accumulation and associated DNA-binding activity. In contrast, several barbiturates, although capable of inducing cytochrome P-450BM-3 and Bm3R1 gene transcription, were unable to induce the Bm3R1 protein. We also demonstrate that cytochrome P-450BM-3 readily oxidizes phytanic acid, and provide evidence that, although the omega-1 hydroxy acid derivatives of phytanic acid can associate with Bm3R1, they do so with an affinity two orders of magnitude lower than the unmodified fatty acid. As a consequence, the ability of the hydroxylated product to induce cytochrome P-450BM-3 gene expression in vivo is markedly reduced. These data collectively suggest that metabolism of fatty acids by cytochrome P-450BM-3 leads to an attenuation of their ability to activate the transcription of the BM-3 operon. This work places the action of bacterial fatty acid hydroxylases in an autoregulatory loop where they may be responsible for the inactivation or clearance of the inducing fatty acid signal.
authors.affiliation: School of Applied Sciences, The Robert Gordon University Aberdeen, St. Andrews Street, Aberdeen, Scotland, U.K.
authors.forename: N
authors.initials: N
authors.lastname: English
authors.forename: C N
authors.initials: CN
authors.lastname: Palmer
authors.forename: W L
authors.initials: WL
authors.lastname: Alworth
authors.forename: L
authors.initials: L
authors.lastname: Kang
authors.forename: V
authors.initials: V
authors.lastname: Hughes
authors.forename: C R
authors.initials: CR
authors.lastname: Wolf
mesh_terms: D001410:Bacillus megaterium / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000378:metabolism*; D001463:Barbiturates / Q000494:pharmacology; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000378:metabolism*; D004790:Enzyme Induction / Q000187:drug effects; D006900:Hydroxylation; D007700:Kinetics; D008830:Microbodies / Q000502:physiology; D006899:Mixed Function Oxygenases / Q000096:biosynthesis / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase; D010084:Oxidation-Reduction; D010424:Pentobarbital / Q000494:pharmacology; D010634:Phenobarbital / Q000494:pharmacology; D010831:Phytanic Acid / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D012631:Secobarbital / Q000494:pharmacology; D013379:Substrate Specificity; D014157:Transcription Factors
chemical_list: D001426:Bacterial Proteins; D001463:Barbiturates; D011743:Pyrimidines; D011994:Recombinant Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C073493:Bm3R1 protein, Bacillus megaterium; D010831:Phytanic Acid; D012631:Secobarbital; C006253:pirinixic acid; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D009251:NADPH-Ferrihemoprotein Reductase; C052423:flavocytochrome P450 BM3 monoxygenases; D010424:Pentobarbital; D010634:Phenobarbital