Monooxygenases

All known P450-containing monooxygenase systems share common structural and functional domain architecture. Apart from P450 itself, these systems can comprise several fundamentally different protein components or domains, all of which are shared by other multicomponent/multidomain enzyme systems with various functions: FAD flavoprotein or domain, FMN domain, Fe2S2 ferredoxin, Fe3S4 ferredoxin, and cytochrome b5. Either FMN domain, ferredoxins or cytochrome bs serve as the electron transport intermediate between the FAD domain and P450. The molecular evolution of both P450-containing systems and of each particular component does not follow phylogeny in general. Gene fusion and horizontal gene transfer events can lead to the appearance of novel redox chains in the same manner that artificial chimeric proteins can be constructed by humans. Recent studies using genetic and protein engineering techniques to investigate the separate domains and their interaction are described.

The choice of bioinorganic motifs by Nature results in a spectacular variety of active-site structures even within the same protein family. Here, we use the concept of the bioinorganic motif to discuss the function and evolution of P450-containing and other related systems. Apart from P450, these systems include a FAD flavoprotein or domain, a FMN domain, ferredoxins and cytochrome b5. Analysis of available complete genomes can shed light on what an ancestral P450-containing system could be.

Microbial oxidation potentials of extremophiles recovered from Pampo Sul oil field, Campos Basin, Brazil, in pure culture or in consortia, were investigated using high-throughput screening (HTS) and multibioreactions. Camphor (1), cis-jasmone (2), 2-methyl-cyclohexanone (3), 1,2-epoxyoctane (4), phenylethyl acetate (5), phenylethyl propionate (6), and phenylethyl octanoate (7) were used to perform multibioreaction assays. Eighty-two bacterial isolates were recovered from oil and formation water samples and those presenting outstanding activities in HTS assays were identified by sequencing their 16S rRNA genes. These results revealed that most microorganisms belonged to the genus Bacillus and presented alcohol dehydrogenase, monooxygenase, epoxide hydrolase, esterase, and lipase activities.

Hepatic microsomes prepared from 10 fish species from Bermuda were studied to establish features of cytochrome P450 (CYP) systems in tropical marine fish. The majority (7/10) of the species had total P450 content between 0.1 and 0.5 nmol/mg, and cytochrome b5 content between 0.025 and 0.25 nmol/mg. Ethoxycoumarin O-deethylase (ECOD) and aminopyrine N-demethylase (APND) rates in these 7 species were 0.23-2.1 nmol/min/mg and 0.5-11 nmol/min/mg, respectively, similar to rates in many temperate fish species. In contrast to those 7 species, sergeant major (Abudefduf saxatilis) and Bermuda chub (Kyphosus sectatrix) had microsomal P450 contents near 1.7 nmol/mg, among the highest values reported in untreated fish, and had greater rates of ECOD, APND, ethoxyresorufin O-deethylase (EROD) and pentoxyresorufin O-depentylase than did most of the other species. Freshly caught individuals of all species had detectable levels of EROD and aryl hydrocarbon hydroxylase (AHH) activities. Those individ...

Twenty five derivatives of the drugs terfenadine and ebastine have been designed, synthesized and evaluated as inhibitors of recombinant human CYP2J2. Compound 14, which has an imidazole substituent, is a good non-competitive inhibitor of CYP2J2 (IC(50)=400nM). It is not selective towards CYP2J2 as it also efficiently inhibits the other main vascular CYPs, such as CYP2B6, 2C8, 2C9 and 3A4; however, it could be an interesting tool to inhibit all these vascular CYPs. Compounds 4, 5 and 13, which have a propyl, allyl and benzo-1,3-dioxole terminal group, respectively, are selective CYP2J2 inhibitors. Compound 4 is a high-affinity, competitive inhibitor and alternative substrate of CYP2J2 (K(i)=160+/-50nM). Compounds 5 and 13 are efficient mechanism-based inhibitors of CYP2J2 (k(inact)/K(i) values approximately 3000Lmol(-1)s(-1)). Inactivation of CYP2J2 by 13 is due to the formation of a stable iron-carbene bond which occurs upon CYP2J2-catalyzed oxidation of 13 with a partition ratio o...

The Directory of P450-containing Systems on World-Wide Web has been designed to facilitate access to electronic resources for all researchers working in the field of P450-containing and related enzyme systems. Currently, it contains the most up-to-date list of sequences of both the P450 superfamily and proteins mediating electron transfer to P450, i.e. NADPH:P450 reductases, specific NAD(P)H:ferredoxin reductases, cytochrome b5 reductases, ferredoxins and cytochromes b5, and their homologues. All the referenced sequences are provided with accession numbers and links to major sequence databanks: PIR, SWISS-PROT, EMBL/GenBank and PRF. An associated database of steroid substrates and products of P450-dependent reactions has also been developed.