摘要:

We provide here a list of 481 P450 genes and 22 pseudogenes, plus all accession numbers that have been reported as of October 18,1995. These genes have been described in 85 eukaryote (including vertebrates, invertebrates, fungi, and plants) and 20 prokaryote species. Of 74 gene families so far described, 14 families exist in all mammals examined to date. These 14 families comprise 26 mammalian subfamilies, of which 20 and 15 have been mapped in the human genome and the mouse genome, respectively. Each subfamily usually represents a cluster of tightly linked genes widely scattered throughout the genome, but there are exceptions. Interestingly, theCYP51family has been found in mammals, filamentous fungi and yeast, and plants - attesting to the fact that this P450 gene family is very ancient. One functionalCYP51gene and two processed pseudogenes, which are the first examples of intronless pseudogenes within the P450 superfamily, have been mapped to three different human chromosomesThis revision supersedes the four previous updates in which a nomenclature system, based on divergent evolution of the superfamily, has been described. For the gene, we recommend that the italicized root symbol'CYP'for human ('Cyp' for mouse and Drosophila), representing 'cytochromeP450' be followed by an Arabic number denoting the family, a letter designating the subfamily (when two or more exist), and an Arabic numeral representing the individual gene within the subfamily. A hyphen is no longer recommended in mouse gene nomenclature.'P'('ps' in mouse and Drosophila) after the gene number denotes a pseudogene;'X'after the gene number means its use has been discontinued. If a gene is the sole member of a family, the subfamily letter and gene number would be helpful but need not be included. The human nomenclature system should be used for all species other than mouse and Drosophila. The cDNAs, mRNAs and enzymes in all species (including mouse) should include all capital letters, and without italics or hyphens. This nomenclature system is similar to that proposed in our previous updates

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Nicotinamide N-methyltransferase (NNMT) catalyses the N-methylation of nicotinamide and other pyridines. Human liver NNMT activity shows large individual variations and a bimodal frequency distribution, raising the possibility that this activity, like those of many other methyltransferase enzymes, might be regulated by a genetic polymorphism. In an attempt to develop an experimental animal model for pharmacogenetic studies of NNMT, we determined optimal conditions for the measurement of hepatic NNMT activity in C57BL/6J mice. Mouse liver NNMT was a cytoplasmic enzyme with a pH optimum of 7.4 and apparent Kmvalues for nicotinamide and S-adenosyl-L-methionine, cosubstrates for the reaction, of 370 and 6.5 μM, respectively. These properties were very similar to those of human liver NNMT, as was the relative sensitivity of the mouse liver enzyme to a series of methyltransferase inhibitors. Hepatic NNMT activity was then measured in tissue from male mice of 10 inbred strains. Average levels of NNMT activity in these strains varied by up to 14-fold and ranged from 1.13 ± 0.18 U per mg protein (mean ± SEM, n=6) for C3H/HeJ mice to 16.0 ± 1.16 U per mg protein in C57BR/cdJ animals. Average hepatic NNMT activities in female mice of six strains in which both sexes were studied varied from five-fold higher than those in males for 'low activity' strains, to not significantly different for 'high activity' strains. A series of properties of NNMT was then compared in hepatic cytosol from male mice of three different strains - one with 'low' (C3H/HeJ), one with 'intermediate' (DBA/2J), and one with 'high' (C57BL/6J) hepatic NNMT activity. There were no striking differences among these three strains in hepatic NNMT pH optimum, substrate kinetics, IC50values for inhibitors, thermal stability or behavior during ion exchange chromatography. The existence of large strain and genderdependent variation in hepatic NNMT activity will make it possible to use inbred mice for studies of the role of inheritance and gender in the regulation of NNMT activity in this species, as well as for studies of the potential pharmacological and toxicological consequences of variation in this important drug-metabolizing enzyme activity

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Syrian hamster acetylation capacity is catalysed by twoN-acetyltransferase isozymes (NAT1 and NAT2). Hamster NAT2 (polymorphic) displays acetylator-genotype dependent activity resulting in high, intermediate, and low activity levels in homozygous rapid, heterozygous and homozygous slow acetylators, respectively. A λgt l0 size-selected genomic library was constructed fromEcoRl-digested homozygous slow acetylator Bio. 82.73/H-Patscongenic hamster DNA and screened with a hamsterNAT1probe. A 4.2 kb Eco RI insert from a positive clone was subcloned into pUC 18 and the intron-freeNAT2coding region was sequenced. TheNAT2coding regions from genomic templates of other homozygous rapid and slow acetylator congenic and inbred hamster lines were amplified by the polymerase chain reaction, cloned, and sequenced. TwoNAT2alleles were found, one (NAT2*15) from each homozygous rapid acetylator line and one (NAT2*16A) from each homozygous slow acetylator line.NAT2*15 contained an 870 bp open reading frame encoding a 290 amino acid protein.NAT2*16A was similar except for two silent (T36C and A633G) and one nonsense (C727T) substitutions yielding a 242 amino acid open reading frame. TheNAT215 andNAT2*16A alleles were expressed in Escherichia coli JM105 and the recombinant proteins were characterized. Electrophoretic mobilities of theNAT2*15 andNAT2*16A recombinant hamster proteins differed and correlated with the theoretical molecular weights calculated from their respective open reading frames. NAT2 16A exhibited 500-to 1000-fold lower maximum velocities compared to NAT2 15 for N-acetylation of all arylamine and hydrazine substrates tested. NAT2 16A also catalysed the metabolic activation of iV-hydroxyarylamines and N-hydroxyarylamides at rates 33- and 23-fold lower than NAT2 15. Intrinsic clearance (Vmax/Km) calculations suggest that N-acetylation of p-aminobenzoic acid and 2-aminofluorene in Syrian hamsters is catalysed primarily by NAT2 (NAT2 15) in rapid acetylators but by NAT1 (NAT1 9) in slow acetylators. These results provide a molecular basis for rapid and slow acetylator phenotype in the Syrian hamster

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

The role of genetic factors in the pathogenesis of agranulocytosis was investigated in agranulocytosis patients by phenotyping for N-acetyltransferase and glucose-6-phosphate polymorphism; by typing for gene products of the major histocompatability complex, ABOand RH-blood groups, and haemoglobins; and by performing cytogenetic analysis of chromosome aberrations. Nine persons were identified as agranulocytosis cases in the period from 1982 to 1987 among the population of Sofia. They were contacted again 10 years after recovery from the disease. Five of them were associated with metamizol (dipyrone) use. The results obtained revealed significant differences between the agranulocytosis patients and the healthy population in the human lymphocyte antigen (HLA) allele frequencies, and in the degree and the frequency of chromosome aberrations. A higher frequency of the HLA24 antigen (relative risk 13.60,p=0.05) and a lower frequency of the DQAl*0501 allele were evident for the ex-agranulocytosis patients as compared to the controls (11% versus 57% respectively,p=0.05). In the patients exposed to metamizol, an A24-B7 haplotype was found with a frequency higher than that in the non-exposed patients and the reference group (p<0.05). The HLA-DQwl antigen and metamizol-related agranulocytosis were evidently associated in all cases (5/5; 100%) in contrast to the patients not exposed to metamizol and the controls. The HL-A2 antigen was absent in four of the five metamizol-associated agranulocytosis cases (20%), while in the control group it was present in 56%. The degree of structural rearrangements (0.62 ± 0.2%) and the frequency of chromosome breakages (7.75 ± 0.68%) in agranulocytosis patients were higher than those in the healthy population (0.3 ± 0.12%,p<0.05 and 1.42 ± 0.27%,p<0.01, respectively). The abnormalities affected predominantly chromosomes 1(1p13), 2(2pl2) and 5(5pl2). No differences were found between the agranulocytosis patients and the healthy population when considering the haemoglobin subtypes, ABO-and RH-blood groups, glucose-6-phosphate dehydrogenase activity and the rates of slow and rapid acetylators

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Of a group of 312 non-Hispanic Caucasians who smoked at least one pack per day, had unsuccessfully attempted to stop smoking, and were free of alcohol or other drug dependence, 48.7% carried the A 2 allele of the DRD2 gene. This was significantly greater than the 25.9% prevalence in the 714 known non-Hispanic Caucasian controls without alcohol or drug abuse,p<10-8, and significantly greater than in a smaller set of our study controls. There was a significant, inverse relationship between the prevalence of the D2A1 allele and the age of onset of smoking,p=0.02, and the maximum duration of time the smokers had been able to quit smoking on their own,p=0.02. These results suggest the DRD2 gene is one of a multifactorial set of risk factors associated with smoking

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

The interactions in vitro of LY307640 with the cytochromes P450 (P450s) were studied using human liver microsomes, specific inhibitors of the P450s, and cDNA expressed enzymes. The kinetics of formation of the two major oxidative metabolites, desmethyl LY307640 and LY307640 sulfone, were determined using two human liver microsomal samples. The kinetic data indicated that high and low affinity sites were present for the production of both metabolites of LY307640. The Km(apparent)and Vmax(apparent)for desmethyl LY3 07640 formation by microsomes from human liver E (HL-E) for the high affinity site were 18.8 ± 4.4μM and 402 ± 52 pmol product/min/mg protein. The high affinity site Km(apparent)and Vmax(apparent)for LY307640 sulfone formation by microsomes from HL-E were 4.4 ±2.1 μ M and 81.8 ± 18 pmol product/min/mg protein. The rates of desmethyl LY307640 and LY307640 sulfone formation by the high affinity site were determined using 14 human liver microsomal samples characterized for P450 marker catalytic activities and immunoquantified levels of the P450s. Rates of formation of desmethyl LY307640 significantly correlated with the immunoquantified levels of CYP 2C19 and the ability of the microsomes to 4'-hydroxylate S-mephenytoin. LY307640 sulfone formation significantly correlated with the immunoquantified levels of CYP 3A and the ability of the microsomes to 1'-hydroxylate midazolam. Inhibition studies and use of expressed cytochrome P450 systems confirmed the correlation data demonstrating that CYP 2C19 catalyzed the formation of desmethyl LY307640 and CYP 3A and catalyzed LY307640 sulfone formation. Further, LY307640 competitively inhibited S-mephenytoin 4'-hydroxylation and midazolam 1'-hydroxylation as did the structurally related compound, omeprazole. For the inhibition of S-mephenytoin 4'-hydroxylation and midazolam 1'-hydroxylation, LY307640 had higher Ki(apparent)values than that of omeprazole. These studies demonstrate that the high affinity enzymes which catalyze the formation of the desmethyl and sulfone metabolites of LY307640 are, respectively, CYP 2C19 and CYP 3A. In addition, the inhibition data suggest that LY307640 has less potential to inhibit the metabolism of CYP 2C19 substrates compared to omeprazole, and that LY307640 and omeprazole have a similarly low potential to inhibit the metabolism of CYP 3A substrates

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Amonafide is extensively metabolized, including conversion by N-acetylation to an active metabolite. Our previous studies have shown that fast acetylators of amonafide have increased toxicity, and we have recommended doses of 250 and 375 mgm-2day-1for 5 days, for fast and slow acetylators, respectively. Despite phenotype-specific dosing, significant variability in leukopenia persisted. The goal of this study was to construct and validate a pharmacodynamic model-based dosing strategy for amonafide, to try to further decrease inter-patient variability in leukopenia. The model was based on a training data set of 41 patients previously treated with amonafide. The first cycle nadir WBC was modelled as a function of dose, acetylator phenotype and baseline patient factors. This model was validated prospectively on patients similar to those in our previous studies. Based on the training data set, the optimal model was defined by three factors: acetylator phenotype, gender, and pretreatment WBC. Using this model and a target WBC nadir of 1700μ 1-1, six dosing strata were prospectively evaluated. A total of 24 fast acetylators received either 238 or 276 mgm-2day-1and 20 slow acetylators received between 345 and 485 mgm-2day-1The mean (±SE) error (deviation from target nadir) was 430 (±240) cells μI-1. Submaximal treatment (yielding grade 0-1 leukopenia) was limited to 20% of patients, while 55% experienced grade 2-3 toxicity. A complex dosing strategy for amonafide is feasible, employing prospective acetylator phenotyping, model-guided dosing, and adaptive control

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

A cytochrome P450 cDNA, encoding a new form of CYP3A protein, was isolated from a liver cDNA library of a male rat using anti-P4506β-1and anti-P4506β-2antibodies and the CYP3A2 cDNA. The cDNA (CYP3A18 cDNA) consisted of 1987 nucleotides, in which were contained an open reading frame of 1491 bp (corresponding to 497 amino acids), 5'-(59bp) and 3'-noncoding regions (437bp). The deduced amino acid sequence of CYP3A18 cDNA was completely identical in the first 27 N-terminal residues of P4506β-2previously isolated by us (Nagata etal.JBiochem 1990:107, 718-72 5) from livers of rats treated with dexamethasone, and also shared higher extents of similarity with hamster CYP3A10 (78.5%) than with rat CYP3As previously sequenced (66.3-69.3%). Northern blot analyses indicated a maledominant expression of this new CYP3AmRNA and enhanced expression in dexamethasoneor pregnenolone-16α carbonitrile (PCN)-treated, but not phenobarbital- or 3-methyIcholanthrene- treated rats. Expressed CYP3A18 protein in COS-1 cells migrated at a position identical to that of purified P4506β-2on sodium dodecyl sulfate-acrylamide gel electrophoresis and catalyzed 16β- and 6-α hydroxylations of testosterone. In contrast to CYP3A1 and CYP3A2, cytochrome b5was not essential for maximal catalytic activities of recombinant CYP3A18 protein. These results, together with ontogenic profiles of CYP3A18 mRNA and P4506β-2protein, indicate that the newly isolated CYP3A18 cDNA encodes P4506β-2in rat liver

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0960-314X    

出版商:OVID    

年代:1996

数据来源: OVID