摘要:

This review focuses upon the regulation of the three human class I alcohol dehydrogenase genes,ADH1,ADH2andADH3. These closely related genes are expressed at high levels in liver, and at different levels in other tissues. Multiplecis-acting sequences to which nuclear proteins bind have been mapped, and transcription factors that can bind to these sequences have been identified; these include C/EBPα, Sp1, USF, HNF1, CTF/NF1, the glucocorticoid receptor, and RARα. There are interesting but often subtle differences in the binding to these three closely related genes, that presumably account for the differences in patterns of their expression.

ISSN:0960-314X    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Over the past 10 years, much fascinating information has been obtained concerning the biochemistry, genetics, toxicological implications and molecular genetics of the N-acetylation polymorphism in mice. Using C57BL/6J (B6) mice as representative of rapid acetylation and A/J (A) mice as representing slow acetylation, it has been shown that the polymorphism observed in N-acetyltransferase (NAT) activity in liver also occurs in kidney, bladder, blood, and other tissues. The development of congenic acetylator mouse lines derived from B6 and A, have provided the necessary tools to study the role of the acetylation polymorphism, on either the B6 or A genetic background, free of nearly all other genetic differences between these strains. Eliminating genes which modify and complicate the differences due to the acetylator genes make the congenic lines very useful in toxicology studies, particularly those involving carcinogenesis.The molecular genetic basis of the acetylator polymorphism in B6 and A mice involves twoNatgenes.Nat-1 encodes a protein termed NAT1 which is identical in rapid and slow acetylator strains.Nat-2, however, differs between rapid and slow strains by a single nucleotide change in the coding region. The corresponding NAT2 proteins differ by a single change at amino acid 99: an hydrophilic asparagine in rapid acetylator NAT2 to an hydrophobic isoleucine in NAT2 from slow acetylators. The mechanistic basis for the difference between rapid and slow acetylation in mice appears to be that NAT2 from the rapid B6 strain is 15-fold more stable at 37° C and is transcribed/translated with a maximal efficiency twice that of the enzyme from slow acetylator A mice.Results discussed in this review indicate that mice provide an excellent system for studying theN-acetyltransferase polymorphism and also are useful for modelling several aspects of the humanN-acetyltransferase polymorphism.

ISSN:0960-314X    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Both guinea pig and rabbit express two variants of the ‘lung’ flavin-containing monooxygenase (FMO), observed as three distinct phenotypes based on mobility differences in SDS-PAGE. Samples of messenger RNA prepared from lungs of the two homozygous phenotypes of the guinea pig were used for the construction of two cDNA libraries. The libraries were screened with a cDNA encoding the rabbit lung FMO, and positive clones for each guinea pig lung FMO variant were isolated and sequenced. A full length clone from each library was found to encode a protein of 535 amino acids containing two pyrophosphate binding sites. Comparison of the sequences of the guinea pig and rabbit lung FMOs shows that their primary structures are 86% identical. The coding region sequences of the guinea pig variants differ at only two positions, and both differences result in amino acid substitutions. Sequence analysis has also been completed on a partially characterized variant of the rabbit lung FMO. As with the guinea pig, the nucleotide and amino acid sequences of the rabbit variants differ at only two positions. The cDNAs encoding the guinea pig variants were expressed in yeast. The activities of the enzymes are characteristic of the lung FMO, and the mobilities of the expressed enzymes are the same as those observed for the variants present in guinea pig pulmonary microsomal preparations. Similar to findings for the rabbit, analysis of genomic DNA indicates that the guinea pig lung FMO is associated with a single gene. The results of cDNA sequence analysis, expression in yeast, and analysis of genomic DNA indicate that the multiple lung FMOs in guinea pig and rabbit are allelic variants whose mobilities in SDS-PAGE are markedly altered by minimal changes in primary structure.

ISSN:0960-314X    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

ArylamineN-acetyltransferase catalyses theN-acetylation of primary arylamine and hydrazine drugs and chemicals.N-acetylation is subject to a polymorphism and humans can be categorized as either fast or slow acetylators according to their ability toN-acetylate polymorphic substrates in vivo. Previously, slow acetylation has been linked to four distinct polymorphicN-acetyltransferase (pnat) alleles each of which contains one or more point mutations within the coding region of thepnatgene. One new rare slow variant ofpnathas been identified by cloning and sequencing thepnatDNA from an individual whose NAT phenotype was determined by in vivo acetylation of the polymorphic substrate sulphamethazine. This allele, designated Sic, differs from the wild type fast allele at nucleotide positions 341 and 803. A second new rare slow allotypic variant, designated S3, has been identified by resistance of thepnatspecific DNA to digestion with the restriction enzymesFokI andBamHI.A method of genotyping individuals for the arylamineN-acetyltransferase (NAT) polymorphism is presented which correctly predicts the phenotype of greater than 95% (21 of 22) of individuals as measured by the extent of acetylation of sulphamethazine in urine. This refined genotyping method was applied to a clinical population of 48 Caucasians with classical or definite rheumatoid arthritis each receiving daily between 150 and 500 mg of the anti-rheumatic drug, D-penicillamine. There is no difference in theN-acetyltransferase phenotype of the individuals who developed proteinuria and the control group with no adverse effects.

ISSN:0960-314X    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

A test designed to estimate the extent and rate of formation of 7-hydroxycoumarin¶ by measuring the urinary excretion of the metabolite in humans after administering 5 mg coumarin was developed. Coumarin was rapidly metabolized after oral administration and more than 95% of the 7OHC formed was excreted in 4h. The total amount of 7OHC formed was 64±5% (mean ± SD, variation 20-100%) of the dose given. The percentage of 7OHC excreted in 2 h, as compared with the 7OHC excretion in 4 h, was found to be a constant and stable individual characteristic for the rate of the formation of 7OHC (‘2 h coumarin test’). In 110 volunteers, there was a great interindividual variability in the extent and rate of 7OHC formation. Four individuals had relatively ‘slow’ coumarin test values (50-60%), but much larger populations would be needed for the demonstration of polymorphism.

ISSN:0960-314X    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The rare H-variant of human butyrylcholinesterase is a quantitative variant that reduces serum butyrylcholinesterase activity by about 90%. Individuals who are heterozygous for both the H-variant and the atypical variant are abnormally sensitive to the muscle relaxant succinylcholine. By using standard phenotypic serum assays, the Danish Cholinesterase Research Unit identified four individuals from two unrelated pedigrees who were heterozygous for both the H-variant (H) and the atypical (A) variant. DNA of these A/H individuals was extracted from white blood cells. Using the polymerase chain reaction and subsequent DNA sequencing, a point mutation was found at nucleotide 424 which changed amino acid 142 from valine to methionine. The previously identified atypical mutation, Asp 70 to Gly, was also seen, which segregated apart from the H-variant mutation in family studies. These two mutations were found in all four A/H individuals.

ISSN:0960-314X    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

After a single oral dose of racemic mephenytoin the S/R ratio in urine can be used to phenotype extensive (EM) and poor metabolizers (PM) of S-mephenytoin. We confirmed the increased S/R ratio by storage time in EM because of the hydrolysis of a conjugate of S-mephenytoin excreted in EM, but not in PM. The S/R ratio in the 0-8 h urine increased 8- to 127-fold (from 0.22 ± 0.16 to 9.9 ±11.3) after acid treatment of urine from 30 EM, but there was no effect of acid in that of 12 PM. We suggest that the phenotype of mephenytoin in combination with debrisoquine can be determined in the 0-8 h urine by estimating the mephenytoin S/R ratio before and after acid treatment.

ISSN:0960-314X    

出版商:OVID    

年代:1992

数据来源: OVID