Mouse alcohol dehydrogenase isozymes: products of closely localized duplicate genes exhibiting divergent kinetic properties

Aldehyde oxidase and alcohol dehydrogenase genetics in the mouse. New alleles for the Aox-2 and Adh-3 loci

The genetic variability of one of the liver isozymes of aldehyde oxidase (AOX-B2 or AOX-2) and the stomach isozyme of alcohol dehydrogenase (ADH-C2) has been examined among strains of mice. Evidence is presented for a fourth allele of Aox-2 and a third allele of Adh-3. The hybrid allozyme pattern for mouse liver AOX was consistent with a dimeric subunit structure for this enzyme.

Alcohol dehydrogenase isozymes in the mouse: genetic regulation, allelic variation among inbred strains and sex differences of liver and kidney A2 isozyme activity

Genetic analysis of a proposed cis-acting temporal locus (Adh-3t), which regulates alcohol dehydrogenase C2 (ADH-C2) activity in mouse epididymis extracts, among F1 (ddN X BALB/c) X ddN male backcross progeny provided evidence for genetic distinctness between the structural (Adh-3) and temporal (Adh-3t) loci on chromosome 3. Genetic analysis also confirmed the close linkage of Adh-1 (encoding liver and kidney ADH-A2) and Adh-3 (encoding stomach ADH-C2) to within 0.3 centimorgans on the mouse genome. Evidence is presented for a proposed closely linked cis-acting temporal locus (designated Adh-lt) for the A2 isozyme (encoded by Adh-1) controlling the activity of this enzyme in mouse kidney extracts, but having no apparent affect on liver and intestine ADH-A2 activities. An extensive survey of the distribution of Adh-1, Adh-3 and Adh-3t alleles among 65 strains of mice is reported--with the exception of two Japanese strains (ddN and KF), linkage disequilibrium between Adh-3 and Adh-3t was observed. Sex differences in mouse liver and kidney ADH-A2 activities were observed, with male/female ratios of approximately 0.6 and 3 respectively for these tissue extracts.

Sorbitol dehydrogenase genetics in the mouse: a 'null' mutant in a 'European' C57BL strain

A 'null' activity variant phenotype for sorbitol dehydrogenase (SDH) was observed in C57BL/LiA mice and used to examine the genetics of this enzyme. Linkage studies of the locus (Sdh-1) with non-agouti (a) and a biochemical locus encoding liver L-alpha-hydroxyacid oxidase (Hao-1) demonstrated that it is coincident with or closely linked to the structural locus, previously localized on chromosome 2. Alcohol dehydrogenase (ADH) isozymes were also examined, since the liver A2 isozyme exhibited some activity as a sorbitol dehydrogenase on cellulose acetate zymograms. It is apparent that SDH activity is not 'essential' in this mouse strain.

Alcohol dehydrogenases and aldehyde dehydrogenases among inbred strains of mice: multiplicity, development, genetic studies and metabolic roles

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are the major enzymes responsible for the metabolism of alcohols and aldehydes in the body. Both exist as a family of isozymes in mammals, and have been extensively studied in animal models, particularly among inbred strains of mice. Mouse ADH exists as at least three major classes, which are predominantly localized in liver (classes I and III), and in stomach/cornea (class IV). Mouse ALDH exhibits extensive multiplicity, several forms of which have been characterized, including ALDH1 (liver cytoplasmic/class 1 isozyme); ALDH2 (liver mitochondrial/class 2.); ALDH3 (stomach cytosolic/class 3); ALDH4 (liver microsomal/class 3); and ALDH5 (testis cytosolic/class 3). Biochemical, genetic and molecular genetic analyses have been performed on several of these enzymes, including studies on variant forms of ADH and ALDH. Distinct metabolic roles are proposed, based upon their tissue and subcellular distribution characteristics and the biochemical properties for these enzymes.

Organization of six functional mouse alcohol dehydrogenase genes on two overlapping bacterial artificial chromosomes

Mammalian alcohol dehydrogenases (ADH) form a complex enzyme system based on amino-acid sequence, functional properties, and gene expression pattern. At least four mouse Adh genes are known to encode different enzyme classes that share less than 60% amino-acid sequence identity. Two ADH-containing and overlapping C57BL/6 bacterial artificial chromosome clones, RP23-393J8 and -463H24, were identified in a library screen, physically mapped, and sequenced. The gene order in the complex and two new mouse genes, Adh5a and Adh5b, and a pseudogene, Adh5ps, were obtained from the physical map and sequence. The mouse genes are all in the same transcriptional orientation in the order Adh4-Adh1-Adh5a-Adh5b-Adh5ps-Adh2-Adh3. A phylogenetic tree analysis shows that adjacent genes are most closely related suggesting a series of duplication events resulted in the gene complex. Although mouse and human ADH gene clusters contain at least one gene for ADH classes I-V, the human cluster contains 3 class I genes while the mouse cluster has two class V genes plus a class V pseudogene.

Metabolic deficiencies in alcohol dehydrogenase Adh1, Adh3, and Adh4 null mutant mice. Overlapping roles of Adh1 and Adh4 in ethanol clearance and metabolism of retinol to retinoic acid

Targeting of mouse alcohol dehydrogenase genes Adh1, Adh3, and Adh4 resulted in null mutant mice that all developed and reproduced apparently normally but differed markedly in clearance of ethanol and formaldehyde plus metabolism of retinol to the signaling molecule retinoic acid. Following administration of an intoxicating dose of ethanol, Adh1 -/- mice, and to a lesser extent Adh4 -/- mice, but not Adh3 -/- mice, displayed significant reductions in blood ethanol clearance. Ethanol-induced sleep was significantly longer only in Adh1 -/- mice. The incidence of embryonic resorption following ethanol administration was increased 3-fold in Adh1 -/- mice and 1.5-fold in Adh4 -/- mice but was unchanged in Adh3 -/- mice. Formaldehyde toxicity studies revealed that only Adh3 -/- mice had a significantly reduced LD50 value. Retinoic acid production following retinol administration was reduced 4.8-fold in Adh1 -/- mice and 8.5-fold in Adh4 -/- mice. Thus, Adh1 and Adh4 demonstrate overlapping functions in ethanol and retinol metabolism in vivo, whereas Adh3 plays no role with these substrates but instead functions in formaldehyde metabolism. Redundant roles for Adh1 and Adh4 in retinoic acid production may explain the apparent normal development of mutant mice.

Alcohol dehydrogenase (ADH) isozymes in the AdhN/AdhN strain of Peromyscus maniculatus (ADH-deermouse) and a possible role of class III ADH in alcohol metabolism

Although the AdhN/AdhN strain of Peromyscus maniculatus (so-called ADH- deermouse) has been previously considered to be deficient in ADH, we found ADH isozymes of Classes II and III but not Class I in the liver of this strain. On the other hand, the AdhF/AdhF strain (so-called ADH+ deermouse), which has liver ADH activity, had Class I and III but not Class II ADH in the liver. In the stomach, Class III and IV ADHs were detected in both deermouse strains, as well as in the ddY mouse, which has the normal mammalian ADH system with four classes of ADH. These ADH isozymes were identified as electrophoretic phenotypes on the basis of their substrate specificity, pyrazole sensitivity, and immunoreactivity. Liver ADH activity of the ADH- strain was barely detectable in a conventional ADH assay using 15 mM ethanol as substrate; however, it increased markedly with high concentrations of ethanol (up to 3 M) or hexenol (7 mM). Furthermore, in a hydrophobic reaction medium containing 1.0 M t-butanol, liver ADH activity of this strain at low concentrations of ethanol (< 100 mM) greatly increased (about sevenfold), to more than 50% that of ADH+ deermouse. These results were attributable to the presence of Class III ADH and the absence of Class I ADH in the liver of ADH- deermouse. It was also found that even the ADH+ strain has low liver ADH activity (< 40% that of the ddY mouse) with 15 mM ethanol as substrate, probably due to low activity in Class I ADH. Consequently, liver ADH activity of this strain was lower than its stomach ADH activity, in contrast with the ddY mouse, whose ADH activity was much higher in the liver than in the stomach, as well as other mammals. Thus, the ADH systems in both ADH- and ADH+ deermouse were different not only from each other but also from that in the ddY mouse; the ADH- strain was deficient in only Class I ADH, and the ADH+ strain was deficient in Class II ADH and down-regulated in Class I ADH activity. Therefore, Class III ADH, which was found in both strains and activated allosterically, may participate in alcohol metabolism in deermouse, especially in the ADH- strain.

Stage and tissue-specific expression of the alcohol dehydrogenase 1 (Adh-1) gene during mouse development

The Adh-1 gene product, ADH-A2, the only known murine class I alcohol dehydrogenase, is able to oxidize retinol (vitamin A) into retinaldehyde, the first enzymatic step in the conversion of retinol into its biologically active metabolite retinoic acid. We have investigated the developmental expression pattern of Adh-1 transcripts by in situ hybridization. Transcripts were first detected by embryonic day 10.5 in the mesonephros mesenchyme. During the following gestational days, Adh-1 transcripts were detected in several mesenchymal areas, such as nasal, laterocervical, and genital regions. Adh-1 transcripts were also detected in a small ectodermal domain at the anterior margins of both forelimbs and hindlimbs. During late fetal development. Adh-1 transcripts were found essentially in the epidermis and in a number of tissues which continue to express the gene after birth, such as liver, kidney, gut epithelium, adrenal cortex, testis interstitium, and ovarian stroma. In contrast, a strong expression of Adh-1 was found in the mesenchyme of developing lungs, but not in the adult organ. This highly regulated expression of Adh-1 is discussed with respect to the local synthesis of retinoic acid during development. Although the promoter of the human counterpart of Adh-1 contains a retinoic acid response element (Duester et al. [1991] Mol. Cell. Biol. 11:1638-1646), we report that this element is not conserved in the murine gene. Consistently, Adh-1 promoter-containing reporter constructs were not retinoic acid-inducible in cotransfections assays with RARs and/or RXRs, suggesting that retinoic acid regulation of Adh-1 differs from that of the human gene.

Multiplication of the class I alcohol dehydrogenase locus in mammalian evolution

Chromosomal DNA samples derived from various primates and other mammals (horse, sheep, rabbit, and mouse) were digested with restriction endonuclease and hybridized with a probe of the sixth exon of the human ADH gene, which is highly conserved in the class I alcohol dehydrogenase of these mammalian species. The copy number of the class I ADH gene in each species was estimated from the number of hybridized bands. Primate DNA samples showed three distinct bands in the blots of PstI digest and DraI digest. Moreover, most of the bands from primate DNA showed a similarity in size so as to allow us to assign the ADH1, ADH2, and ADH3 homologues in each species. In contrast, mouse has only one gene, and rabbit, sheep, and horse seem to have only two genes, for the class I ADH, which showed divergent hybridization bands. These results are consistent with the view that the human class I ADH gene cluster has been generated through gene multiplication events which occurred before the Catarrhini branch point in the course of primate evolution.

Tissue-specific genetic variation in the level of mouse alcohol dehydrogenase is controlled transcriptionally in kidney and posttranscriptionally in liver

Tissue-specific genetic variation in expression of the alcohol dehydrogenase, encoded by the Adh-1 gene, is found between C57BL/6J (B6) mice and B6.S congenic mice. B6.S mice contain a variant Adh-1 allele derived from a wild Danish strain in a B6 genetic background. B6 mice have nearly twice the alcohol dehydrogenase activity in liver but less than half the activity in kidney as B6.S mice. These tissue-specific genetic changes in alcohol dehydrogenase expression are manifest at the level of Adh-1-encoded mRNA. The regulatory site(s) involved act cis in both kidney and liver. These strains also differ in the extent to which androgen induces mRNA encoded by kidney Adh-1, with androgen increasing these levels 17-fold and 7.4-fold in the B6 and B6.S kidney, respectively. To identify the regulatory mechanism(s) underlying this strain variation in Adh-1 transcription in the B6 and B6.S kidney, liver, and androgen-induced kidney. For both uninduced and induced kidney, a difference in the transcription rate alone accounts for the strain difference in mRNA concentration. In contrast, because the Adh-1 transcription rate in liver does not differ significantly between B6 and B6.S mice, strain-specific variation in posttranscriptional regulation must be operative. Taken together these results indicate that the variation in Adh-1 expression between B6 and B6.S mice results from changes in both transcriptional and posttranscriptional control, and these controls are differentially operative in kidney and liver.

Purification and characterization of the Danish (Skive) variant of mouse liver alcohol dehydrogenase

The partially inbred Danish (Skive) strain of mice exhibits a form of liver alcohol dehydrogenase (ADH) which differs in electrophoretic mobility from that of all other inbred mouse strains thus far examined, e.g., C57BL/10, DBA/2J, and BALB/c. In order to compare the catalytic and molecular properties of the "variant" and "normal" enzyme forms, they were purified to homogeneity by ion-exchange and affinity chromatography. Tryptic peptides of reduced and carboxymethylated subunits of the normal and variant ADH forms were mapped by thin-layer two-dimensional electrophoresis and chromatography and by reversed-phase high-performance liquid chromatography. A unique nonapeptide in the Danish mouse liver ADH which did not appear in enzymes from C57BL/10, DBA/2J, or BALB/c mice was identified by both methods. Amino acid sequencing of this peptide revealed that the Arg residue at position 124, as predicted from the cDNA sequence of ADH in DBA/2J mice, has been replaced by Leu in the Danish variant. The Leu for Arg substitution in the variant form appears to account for its decreased cathodic mobility with electrophoresis in starch gels at pH 7.2. The Km and Vmax of ADH from the Danish strain for three primary alcohols and three aldehydes were similar in value to those of ADH from the C57BL/10, DBA/2J, and BALB/c strains. Based on the X-ray structure of horse liver ADH, position 124 is on the solvent-exposed surface of the catalytic domain. The finding that the kinetic constants are similar for the normal and variant forms is consistent with the observation that this residue is not in the active site and that there is no known role for it in the ADH catalytic mechanism.

Molecular analysis of mouse alcohol dehydrogenase: nucleotide sequence of the Adh-1 gene and genetic mapping of a related nucleotide sequence to chromosome 3

The mouse has three genes (Adh) encoding alcohol dehydrogenase (ADH) enzymes of different tissue specificity and catalytic properties. Identified regulatory loci are known to affect the expression of Adh-1 and Adh-3, which are closely linked on chromosome 3. The Adh-1 gene product is expressed predominantly in liver, and its mRNA product is androgen-inducible in kidney. In this study, genomic clones of Adh-1 were obtained from a Balb/cJ DNA library. The nucleotide sequences of all exons, intron/exon boundaries and 5'- and 3'-flanking regions were obtained. The gene spans nearly 13 kb and is divided into nine exons and eight introns. The transcription start point of this gene was determined by S1 nuclease mapping studies and presumptive regulatory regions in the 5'-flanking regions were identified, including a TATA box and a glucocorticoid-responsive element. A restriction fragment length polymorphism in the Adh-1 gene was identified among inbred strains and mapped at the [Adh-1, Adh-3] complex on chromosome 3. An additional 'Adh-like' sequence in the genome was also mapped to chromosome 3 approx. 9 centiMorgans from Adh-1.

Alcohol dehydrogenase isozymes in baboons: tissue distribution, catalytic properties, and variant phenotypes in liver, kidney, stomach, and testis

Isoelectric focusing and cellulose acetate electrophoresis were used to examine the multiplicity, tissue distribution, and variability of alcohol dehydrogenase (ADH) among baboons, a primate species used as a model for research on alcohol metabolism and alcohol-induced liver pathology. Five major ADH isozymes were resolved and distinguished on the basis of their isoelectric points, tissue distributions, relative activities with alcohol substrates, and sensitivities to inhibition with 4-methyl pyrazole. ADH-1 and ADH-2 exhibited class I kinetic properties and were observed in high activity in kidney and liver extracts, respectively. ADH-3 showed class II kinetic properties, exhibiting high activity in stomach extracts, and was widely distributed in extracts of other baboon tissues, including kidney, esophagus, heart, testis, brain, and male sex accessory tissues. ADH-4 also showed class II ADH properties but was found only in liver (similar to human "pi-ADH"). ADH-5 exhibited class III ADH kinetic properties, being inactive with ethanol up to 0.5 M (similar to human "chi-ADH") and was distributed widely in baboon tissue extracts. Major activity variation was observed for liver ADH-4 between different animals. An electrophoretic variant for ADH-3 was observed for the enzyme in stomach, kidney, and testis extracts, and activity variation existed for this isozyme in kidney extracts. It is apparent that baboon ADH shares a number of features with the human ADH phenotype; however, several species-specific differences were observed, particularly for the liver and kidney class I isozymes and for stomach ADH.

Androgen induction of alcohol dehydrogenase in mouse kidney. Studies with a cDNA probe confirmed by nucleotide sequence analysis

A cDNA clone for the beta-chain of human alcohol dehydrogenase (ADH) was used to isolate several cross-hybridizing clones from a mouse liver cDNA library. Clones pADHm9 and a portion of pADHm12 were sequenced. pADHm9 coded for a sequence of 151 C-terminal amino acids and some untranslated sequences from the 3' end of its corresponding mRNA. This clone was identified as an Adh-1 cDNA clone. Consistent with the known expression of Adh-1, this gene was expressed constitutively in liver, whereas the Adh-3 gene product was found only in stomach, lung and reproductive tissues. Furthermore, the translated region of the cDNA shared 91% amino acid sequence homology with rat liver ADH. [32P]pADHm9 was used as a hybridization probe to study the mechanism of androgen induction of kidney ADH activity. Induction of A/J female mice by androgen resulted in a dramatic increase in the steady-state level of Adh-1 mRNA content which correlated with the level of enzyme induction. The size of the mRNA obtained from control or induced kidney and liver tissues was indistinguishable by Northern analysis. [32P]pADHm9 was also used to probe restriction fragments of genomic DNA obtained from several inbred mouse strains. The hybridization patterns, considered with the genetic evidence, suggested that pADHm9 recognized sequences which may be present as only a single copy in the genome. No restriction fragment length polymorphisms were observed among the several inbred mouse strains examined.

Genetic variants of enzymes of alcohol and aldehyde metabolism

The distribution of genetic variants (or gene markers) for alcohol dehydrogenase, aldehyde dehydrogenase, aldehyde oxidase, and aldehyde reductase isozymes has been examined among 12 inbred strains of mice. Electrophoretic variants are described for the major liver and stomach alcohol dehydrogenase isozymes (ADH-A2 and C2); liver, kidney, and stomach aldehyde dehydrogenase isozymes (AHD-1; AHD-2; AHD-4); a liver-specific aldehyde reductase (AHR-A2); and a liver aldehyde oxidase isozyme (AOX-2). Genetically determined activity variants were observed for a testis-specific aldehyde dehydrogenase (AHD-6); liver and kidney aldehyde reductase isozymes (AHR-3 and AHR-4); and the major liver AOX isozyme (AOX-1). These variants may serve as useful gene markers in alcohol research involving animal model studies with inbred strains in mice.

Interferon-induced guanylate-binding proteins: mapping of the murine Gbp-1 locus to chromosome 3

GBP-1 is the predominant species of a family of guanylate-binding proteins synthesized in mouse cells in response to interferons (IFNs) alpha, beta, or gamma. IFN inducibility of this 65,000-Da protein is controlled by alleles at a single autosomal locus, Gbp-1, with allele a encoding inducibility and allele b noninducibility. Here, we present evidence suggesting that both alleles occur in outbred populations of wild mice. Using recombinant inbred strains and classical linkage analysis of offspring of two-point and three-point backcrosses we demonstrate that Gbp-1 is linked to Adh-3 (encoding alcohol dehydrogenase C2) and VaJ (varitintwaddler-Jackson) located on the distal part of chromosome 3. The relevant recombination frequencies (RFs) (+/- SE) were 3.5 (+/- 1.1) and 11.7 (+/- 2.8)%, respectively. We further show that strain B6.C-H-23c/By(HW 53), congenic for a small segment of chromosome 3, carries the BALB/c alleles at both the Gbp-1 and the Adh-3 locus and not the alleles of the B6 background strain confirming the chromosomal location and close linkage of the two loci.

An isozyme-specific selective system for the recovery of mammalian cells deficient in hepatic alcohol dehydrogenase activity

A selective system toxic towards mammalian cells expressing the liver-specific isozyme of alcohol dehydrogenase (L-ADH) has been developed. A number of alpha-unsaturated primary and secondary alcohols were assayed for their ability to serve as substrates for rat liver ADH and were screened for cytotoxicity towards L-ADH+ and L-ADH- cells. 1-Propen-3-ol and 1-penten-3-ol were identified as agents showing selective cytotoxicity. Reconstruction experiments demonstrated that 1-propen-3-ol at a concentration of 15 microM could be used to recover L-ADH- clones from mixed populations of L-ADH+ and L-ADH cells. Cells expressing the non-allelic S-ADH isozyme were not killed under these conditions. The selective system defined in this report is thus isozyme-specific.

Purification and characterization of mouse alcohol dehydrogenase from two inbred strains that differ in total liver enzyme activity

Alcohol dehydrogenase activity in mouse liver homogenate-supernatants is 1.7 times greater in the C57BL/10 strain than in the BALB/c strain, regardless of whether activity is expressed in units per gram liver, total liver, or milligram DNA. The Km values for ethanol and NAD+, approximately 0.4 and 0.03 mM, respectively, of enzyme purified from both strains are similar. Moreover, the Ki for NADH, 1 microM, the pH optimum for ethanol oxidation, 10.5, and the Vmax for ethanol oxidation, 160 min-1, for ADH from the C57BL/10 and BALB/c strains are similar. Therefore, the difference in ADH activity in the two strains cannot be due to differences in the catalytic properties of the enzyme. The electrophoretic and isoelectric focusing patterns and two-dimensional tryptic peptide maps of the purified enzyme from both strains are identical. Thus the amino acid sequences of enzyme from C57BL/10 and BALB/c mice must also be identical or very similar. The difference in ADH activity in the two strains is most likely the result of genetic differences in the content of ADH protein in liver.

Purification and molecular properties of mouse alcohol dehydrogenase isozymes

Alcohol dehydrogenase isozymes from mouse liver (A2 and B2) and stomach (C2) tissues have been purified to homogeneity using triazine-dye affinity chromatography. The enzymes are dimers with similar but distinct subunit sizes, as determined by SDS/polyacrylamide gel electrophoresis: A, 43000; B, 39000, and C, 47000. Zinc analyses and 1,10-phenanthroline inhibition studies indicated that the A and C subunits each contained two atoms of zinc, with at least one being involved catalytically, whereas the B subunit probably contained a single non-catalytic zinc atom. The isozymes exhibited widely divergent kinetic characteristics. A2 exhibited a Km value for ethanol of 0.15 mM and a broad substrate specificity, with Km values decreasing dramatically with an increase in chain length; C2 also exhibited this broad specificity for alcohols but showed a Km value of 232 mM for ethanol. These isozymes also showed broad substrate specificities as aldehyde reductases. In contrast, B2 showed no detectable activity as an aldehyde reductase for the aldehydes examined, and used ethanol as substrate only at very high concentrations (greater than 0.5 M). The isozyme exhibited low Km and high Vmax values, however, with medium-chain alcohols. Immunological studies showed that A2 was immunologically distinct from the B2 and C2 isozymes. In vitro molecular hybridization studies gave no evidence for association between the alcohol dehydrogenase subunits. The results confirm genetic analyses [Holmes, Albanese, Whitehead and Duley (1981) J. Exp. Zool. 215, 151-157] which are consistent with at least three structural genes encoding alcohol dehydrogenase in the mouse and confirm the role of the major liver isozyme (A2) in ethanol metabolism.

Kinetic properties of human liver alcohol dehydrogenase: oxidation of alcohols by class I isoenzymes

Class I isoenzymes of alcohol dehydrogenase (ADH) were isolated by chromatography of human liver homogenates on DEAE-cellulose, 4-[3-[N-(6-aminocaproyl)-amino]propyl]pyrazole--Sepharose and CM-cellulose. Eight isoenzymes of different subunit composition (alpha gamma 2, gamma 2 gamma 2, alpha gamma 1, alpha beta 1, beta 1 gamma 2, gamma 1 gamma 1, beta 1 gamma 1, and beta 1 beta 1) were purified, and their activities were measured at pH 10.0 by using ethanol, ethylene glycol, methanol, benzyl alcohol, octanol, cyclohexanol, and 16-hydroxyhexadecanoic acid as substrates. Values of Km and kcat for all the isoenzymes, except beta 1 beta 1-ADH, were similar for the oxidation of ethanol but varied markedly for other alcohols. The kcat values for beta 1 beta 1-ADH were invariant (approximately 10 min-1) and much lower (5-15-fold) than those for any other class I isoenzyme studied. Km values for methanol and ethylene glycol were from 5- to 100-fold greater than those for ethanol, depending on the isoenzyme, while those for benzyl alcohol, octanol, and 16-hydroxyhexadecanoic acid were usually 100-1000-fold lower than those for ethanol. The homodimer beta 1 beta 1 had the lowest kcat/Km value for all alcohols studied except methanol and ethylene glycol; kcat values were relatively constant for all isoenzymes acting on all alcohols, and, hence, specificity was manifested principally in the value of Km. Values of Km and kcat/Km revealed for all enzymes examined that the short chain alcohols are the poorest while alcohols with bulky substituents are much better substrates. The experimental values of the kinetic parameters for heterodimers deviate from the calculated average of those of their parent homodimers and, hence, cannot be predicted from the behavior of the latter. Thus, the specificities of both the hetero- and homodimeric isoenzymes of ADH toward a given substrate are characteristics of each. Ethanol proved to be one of the "poorest" substrates examined for all class I isoenzymes which are the predominant forms of the human enzyme. On the basis of kinetic criteria, none of the isoenzymes of class I studied oxidized ethanol in a manner that would indicate an enzymatic preference for that alcohol.

Differential regulation of duplicate alcohol dehydrogenase genes in Drosophila mojavensis

These studies report the existence of multiple forms of alcohol dehydrogenase in extracts of Drosophila mojavensis. The existence of these forms can be best explained by the hypothesis of a duplication for the Adh locus in D. mojavensis. Electrophoretic variants at each locus have been identified and crosses between individuals carrying alternative alleles at each locus result in F1 progeny with six bands of ADH. This pattern is consistent with these individuals being heterozygous at two loci. The loci have been named Adh-1 and Adh-2. Examination of the isozyme content during development shows that the two Adh genes are not coordinately controlled but have separate developmental programs. In embryos and first and second instar larvae only Adh-1 is expressed. At about the time of the second molt Adh-2 expression commences in some of the same cells that previously expressed and continue to express Adh-1. This is evidenced by the existence of an interlocus heterodimer in third instar larvae. Both genes are expressed throughout pupation. Shortly after emergence Adh-1 expression declines. In mature males only ADH-2 is present. In mature females both Adh-1 and Adh-2 are expressed but not in the same cells since the interlocus heterodimer is absent. Examination of specific tissues reveals that most of the larval ADH is found in fat body cells and as in most tissues of third instar larvae both Adh-1 and Adh-2 are expressed. The single exception appears to be larval gut which contains ADH-1 but little if any ADH-2. In mature males and female flies all ADH containing tissues have only ADH-2. However, mature ovaries contain substantial quantities of ADH-1 which is apparently deposited into eggs. Given the extensive amount of available information on the Adh gene-enzyme system of D. melanogaster and the tools that can be applied to the analysis of homologous systems, the ADH duplication of D. mojavensis, and its regulation may be a useful one for studying differential gene regulation in specific cell types.

Alcohol dehydrogenase in the mouse epididymis. Genetic variation and cellular localization

The cellular localization of alcohol dehydrogenase (ADH) in the mouse epididymis was investigated using differential substrate specificities and genetic variation as a means of distinguishing these enzymes histochemically in tissue sections. ADH-C2 exhibited high activity in BALB/c epididymis and was observed as a discrete zone within duct epithelial cells near the nuclei. This isozyme exhibited no detectable activity in C57BL/6J epididymis extracts or histochemical sections.

Purification and properties of sorbitol dehydrogenase from mouse liver

1. The sorbitol dehydrogenase (L-iditol: NAD oxidoreductase, EC 1.1.1.14) from mouse liver has been purified to homogeneity. 2. The enzyme has a mol. wt of 140,000 and is composed of four identical subunits of mol. wt 35,000. 3. the purified enzyme catalyses both sorbitol oxidation and fructose reduction. 4. It is specific for NAD+ (NADH) and does not function with NADP+ (NADPH). 5. The Michaelis constants for sorbitol, fructose, NAD+ and NADPH are 1.54 and 154 mM, 58.8 and 15 microM, respectively. 6. The enzyme is SH-group reagent sensitive and is strongly inhibited by 1,10-phenanthroline.

Biochemical genetics of aldehyde reductase in the mouse: Ahr-1--a new locus linked to the alcohol dehydrogenase gene complex on chromosome 3

Electrophoretic and activity variants for a liver aldehyde reductase (AHR-A2) among strains of Mus musculus have been used in genetic analyses to demonstrate close linkage between the locus encoding this enzyme (designated Ahr-1) and the alcohol dehydrogenase gene complex on chromosome 3. No recombinants were observed between Adh-3 (encoding alcohol dehydrogenase C2; ADH-C2) and Ahr-1 among 42 backcross animals. Moreover, linkage disequilibrium between these loci was observed among 58 of 60 strains of mice examined and among seven recombinant inbred strains derived from C57BL/6J and BALB/c mice. Liver hexonate dehydrogenase (HDH-A) was electrophoretically invariant among the strains examined. Gel filtration analyses demonstrated that AHR-A2 and HDH-A had native molecular weights of approximately 80,000 and 32,000, respectively. Three-banded allozyme patterns for AHR-A2 in CBA/H x castaneus hybrid animals were consistent with a dimeric subunit structure. Comparative substrate and coenzyme specificities for AHR-A2, HDH-A, and ADH-A2 (liver ADH isozyme) were examined. AHR-A2 exhibited a defined specificity toward p-nitrobenzaldehyde as substrate, whereas the other enzymes exhibited broad specificities toward various aliphatic, aromatic, and monosaccharide aldehydes. It is proposed that Ahr-1 is a product of a gene duplication event during mammalian evolution of the primordial mammalian Adh locus and that considerable divergence in catalytic properties has subsequently occurred.