Linked Life Data

9730826

Source:http://linkedlifedata.com/resource/pubmed/id/9730826

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
36
pubmed:dateCreated
1999-2-5
pubmed:abstractText
Cytochromes P450 3A4 and 3A5, the dominant drug-metabolizing enzymes in the human liver, share >85% primary amino acid sequence identity yet exhibit different regioselectivity toward aflatoxin B1 (AFB1) biotransformation [Gillam et al., (1995) Arch. Biochem. Biophys. 317, 374-384]. P450 3A4 apparently prefers AFB1 3alpha-hydroxylation, which results in detoxification and subsequent elimination of the hepatotoxin, over AFB1 exo-8,9-oxidation. In contrast, P450 3A5 is incapable of appreciable AFB1 3alpha-hydroxylation and converts it predominantly to the exo-8,9-oxide which is genotoxic. To elucidate the structural features that govern the regioselectivity of the human liver 3A enzymes in AFB1 metabolism and bioactivation, a combination of approaches including sequence alignment, homology modeling, and site-directed mutagenesis was employed. Specifically, the switch in AFB1 regioselectivity was examined after individual substitution of the divergent amino acids in each of the six putative substrate recognition sites (SRSs) of P450 3A4 with the corresponding amino acid of P450 3A5. Of the P450 3A4 mutants examined, P107S, F108L, N206S, L210F, V376T, S478D, and L479T mutations resulted in a significant switch of P450 3A4 regioselectivity toward that of P450 3A5. The results confirmed the importance of some of these residues in substrate contact in the active site, with residue N206 (SRS-2) being critical for AFB1 detoxification via 3alpha-hydroxylation. Moreover, the P450 3A4 mutant N206S most closely mimicked P450 3A5, not only in its regioselectivity of AFB1 metabolism but also in its overall functional capacity. Furthermore, the other SRS-2 mutant, L210F, also resembled P450 3A5 in its overall AFB1 metabolism and regioselectivity. These findings reveal that a single P450 3A5 SRS domain (SRS-2) is capable of conferring the P450 3A5 phenotype on P450 3A4. In addition, some of these P450 3A4 mutations that affected AFB1 regioselectivity had little influence on testosterone 6beta-hydroxylation, thereby confirming that each substrate-P450 active site fit is indeed unique.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
8
pubmed:volume
37
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
12536-45
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:9730826-Aflatoxin B1, pubmed-meshheading:9730826-Amino Acid Sequence, pubmed-meshheading:9730826-Animals, pubmed-meshheading:9730826-Aryl Hydrocarbon Hydroxylases, pubmed-meshheading:9730826-Binding Sites, pubmed-meshheading:9730826-Computer Simulation, pubmed-meshheading:9730826-Cytochrome P-450 CYP3A, pubmed-meshheading:9730826-Cytochrome P-450 Enzyme System, pubmed-meshheading:9730826-Cytochromes b5, pubmed-meshheading:9730826-Humans, pubmed-meshheading:9730826-Male, pubmed-meshheading:9730826-Microsomes, Liver, pubmed-meshheading:9730826-Models, Molecular, pubmed-meshheading:9730826-Molecular Sequence Data, pubmed-meshheading:9730826-Mutagenesis, Site-Directed, pubmed-meshheading:9730826-NADPH-Ferrihemoprotein Reductase, pubmed-meshheading:9730826-Oxidoreductases, N-Demethylating, pubmed-meshheading:9730826-Rats, pubmed-meshheading:9730826-Recombinant Proteins, pubmed-meshheading:9730826-Stereoisomerism, pubmed-meshheading:9730826-Steroid Hydroxylases, pubmed-meshheading:9730826-Structure-Activity Relationship
pubmed:year
1998
pubmed:articleTitle
Structure-function relationships of human liver cytochromes P450 3A: aflatoxin B1 metabolism as a probe.
pubmed:affiliation
Department of Cellular and Molecular Pharmacology, Liver Center, University of California, San Francisco 94143, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.