Electrophoretic analyses of alcohol dehydrogenase, aldehyde dehydrogenase, aldehyde reductase, aldehyde oxidase and xanthine oxidase from horse tissues

Cellulose acetate zymograms of alcohol dehydrogenase (ADH), aldehyde dehydrogenase (AHD), aldehyde reductase (AHR), aldehyde oxidase (AOX) and xanthine oxidase (XOX) extracted from horse tissues were examined. Five ADH isozymes were resolved: three corresponded to the previously reported class I ADHs (EE, ES and SS) (Theorell, 1969); a single form of class II ADH (designated ADH-C2) and of class III ADH (designated ADH-B2) were also observed. The latter isozyme was widely distributed in horse tissues whereas the other enzymes were found predominantly in liver. Four AHD isozymes were differentially distributed in subcellular preparations of horse liver: AHD-1 (large granules); AHD-3 (small granules); and AHD-2, AHD-4 (cytoplasm). AHD-1 was more widely distributed among the horse tissues examined. Liver represented the major source of activity for most AHDs. A single additional form of NADPH-dependent AHR activity (identified as hexonate dehydrogenase), other than the ADHs previously described, was observed in horse liver. Single forms of AOX and XOX were observed in horse tissue extracts, with highest activities in liver.     

Biochemical genetics of aldehyde dehydrogenase isozymes in the mouse: Evidence for stomach- and testis-specific isozymes

Electrophoretic and activity variants have been observed for stomach and testis aldehyde dehydrogenases, respectively, among inbred strains of the house mouse (Mus musculus). Genetic evidence was obtained for two new loci encoding these isozymes (designated Ahd-4 and Ahd-6, respectively, for the stomach and testis isozymes) which segregated independently of a number of mouse gene markers, including Ahd-1 (encoding mitochondrial aldehyde dehydrogenase) on chromosome 4, ep (pale ears), a marker for chromosome 19, on which Ahd-2 (encoding liver cytosolic aldehyde dehydrogenase) has been previously localized, and Adh-3 (encoding the stomach-specific isozyme of alcohol dehydrogenase) on chromosome 3. Recombination studies have indicated, however, that Ahd-4 and Ahd-6 are distinct but closely linked loci on the mouse genome. An extensive survey of the distribution of Ahd-1, Ahd-2, Ahd-4, and Ahd-6 alleles among 56 strains of mice is reported. No variants have been observed, so far, for the microsomal (AHD-3) and mitochondrial/cytosolic (AHD-5) isozymes previously described. This study, in combination with previous investigations on mouse aldehyde dehydrogenases, provides evidence for six genetic loci for this enzyme.     

Genetics of ocular NAD+-dependent alcohol dehydrogenase and aldehyde dehydrogenase in the mouse: Evidence for genetic identity with stomach isozymes and localization ofAhd-4 on chromosome 11 near trembler

Electrophoretic and activity variation of the stomach and ocular isozyme of aldehyde dehydrogenase (designated AHD-4) was observed between C57BL/6J and SWR/J inbred strains of mice. The phenotypes were inherited in a normal mendelian fashion, with two alleles at a single locus (Ahd-4) showing codominant expression. The alleles assorted independently of those atAdh-3 [encoding the stomach and ocular isozyme of alcohol dehydrogenase (ADH-C₂)] on chromosome 3. Three chromosome 11 markers, hemoglobin -chain (Hba), trembler (Tr), and rex (Re), were used in backcross analyses which established thatAhd-4 is closely linked to trembler. The distribution patterns for stomach and ocular AHD-4 phenotypes were examined among SWXL recombinant inbred mice, and those for stomach and ocular ADH-C₂ among BXD recombinant inbred strains. The data provided evidence for the genetic identity of stomach and ocular ADH-C₂ and of stomach and ocular AHD-4.This research was supported in part by the U.S. Department of Energy under Contract DE-ACO5-84OR214000 with Martin Marietta Energy Systems, Inc. (to R.A.P.).     

Genetics and ontogeny of aldehyde dehydrogenase isozymes in the mouse: Localization of Ahd-1 encoding the mitochondrial isozyme on chromosome 4

Electrophoretic variants for the mitochondrial isozyme of aldehyde dehydrogenase (AHD) have been observed in inbred strains and in Harwell linkage testing stocks of Mus musculus. F₁ (LVC×C57BL/Go) mice showed a codominant allele three-banded phenotype, which suggests a dimeric subunit structure (designated AHD-A₂). The anodal-migrating supernatant isozyme of AHD was electrophoretically invariant among the 23 inbred strains and stocks examined. The genetic locus encoding AHD-A₂ (suggested name Ahd-1) is localized on chromosome 4 and was mapped close to je (jerker) and Gpd-1 (encoding the liver and kidney isozyme of glucose-6-phosphate dehydrogenase). Ontogenetic analyses demonstrated that both AHD isozymes exhibited low activity in late fetal and early neonatal liver and kidney extracts, and reached adult levels within 3 weeks of birth.     

Electrophoretic analyses of alcohol dehydrogenase, aldehyde dehydrogenase, aldehyde oxidase, sorbitol dehydrogenase and xanthine oxidase from mouse tissues.

1. Cellulose acetate zymograms of alcohol dehydrogenase (ADH), aldehyde dehydrogenase, sorbitol dehydrogenase, aldehyde oxidase, "phenazine" oxidase and xanthine oxidase extracted from tissues of inbred mice were examined. 2. ADH isozymes were differentially distributed in mouse tissues: A2--liver, kidney, adrenals and intestine; B2--all tissues examined; C2--stomach, adrenals, epididymis, ovary, uterus, lung. 3. Two NAD+-specific aldehyde dehydrogenase isozymes were observed in liver and kidney and differentially distributed in other tissues. Alcohol dehydrogenase, aldehyde oxidase, "phenazine" oxidase and xanthine oxidase were also stained when aldehyde dehydrogenase was being examined. 4. Two aldehyde oxidase isozymes exhibited highest activities in liver. 5. "Phenazine oxidase" was widely distributed in mouse tissues whereas xanthine oxidase exhibited highest activity in intestine and liver extracts. 6. Genetic variants for ADH-C2 established its identity with a second form of sorbitol dehydrogenase observed in stomach and other tissues. The major sorbitol dehydrogenase was found in high activity in liver, kidney, pancreas and male reproductive tissues.     

Mouse aldehyde dehydrogenase genetics: Positioning of Ahd-1 on chromosome 4

Electrophoretic variants of mitochondrial aldehyde dehydrogenase (AHD-A₂) are widely distributed among inbred strains of Mus musculus and have been used to localize the gene encoding AHD-A₂(Ahd-1) at the non-centromeric end of chromosome 4. In the mouse (Mus musculus), aldehyde dehydrogenase (AHD; E.C.1.2.1.3) exists as at least three isozymes which are differentially distributed in liver subcellular fractions (designated A₂, B₄ and Cy* for the mitochondrial, soluble and microsomal isozymes respectively) and in various tissues of this animal (Holmes, 1978a; 1978b; Timms & Holmes, 1981). Electrophoretic variants have been previously reported for the A₂ and B₄ isozymes among inbred strains of mice, and the genetic loci (designated Ahd-1 and Ahd-2) have been localized on chromosomes 4 and 19 respectively (Holmes, 1978b; Timms & Holmes, 1980). This paper describes further genetic analyses of AHD-A₂ enabling Ahd-1 to be positioned at the non-centromeric end of chromosome 4. Forty-three inbred strains of Mus musculus were used in these studies (Table 1). Two series of matings were carried out. 1) Female SM/J mice and male NZC/B1 mice were mated to obtain F, female offspring which were backcrossed to male NZC/B1 mice. These progeny were used to examine the segregation and linkage relationship of b (brown), Pgm-2 (encoding phosphoglucomutase B) and Ahd-1 (Table 2). 2) Female C57BL/6J mice and male SM/J. mice were mated to obtain F, female offspring which were backcrossed to male SM/J mice. The segregation and linkage relationship of Pgm-2, Gpd-1 (encoding the liver and kidney isozyme of hexose-6 phosphate dehydrogenase) and Ahd-1 were examined for these backcross progeny (Table 3). Methods for preparing liver and kidney extracts and the cellulose acetate electrophoresis procedure for typing Ahd-1, Pgm-2 and Gpd-1 have been previously described (Holmes, 1978b). A previous study has described the electrophoretic patterns for allelic variants for mitochondria1 AHD and of the hybrid phenotype for this enzyme (Holmes, 1978b). The three-allelic isozyme pattern for hybrid animals was consistent with a dimeric subunit structure: AHD-A¹A², AHD-A¹A² and AHD-3, with the A1 and A2 subunits being encoded by separate alleles at a single locus, designated Ahd-1 (Ahd-1^oand Ahd-1^brespectively). The distribution of these alleles among 43 inbred strains of mice is given in Table 1. The allelic variants were approximately equally distributed among the inbred strains examined and no divergence of phenotype was observed among the 6 substrains of C57BL mice (Ahd-1^aallele) and 5 substrains of BALB/c (Ahd-1^ballele) mice examined. Genetic variants for phosphoglucomutase-B (PGM-B) have been reported by Shows, Ruddle and Roderick (1969) and the gene (Pgm-2) was subsequently localized on chromosome 4 near b (brown) by Chapman, Ruddle and Roderick (1970). Table 2 illustrates the results of a three-point cross between b, Pgm-2 and Ahd-1. Variation from the expected 1:1:1:1:1:1 ratio for unlinked loci was significant(x²= 73.15; 7 df; P < 1 × 10^-5), indicating that the three loci are linked. Recombination frequency data are consistent with the gene order: b - Pgm-2 - Ahd-1 The second cross examined the segregation of Pgm-2, Ahd-1 and Gpd-1 loci (Table 3). The latter locus has been previously positioned on chromosome 4 (linkage group VIII) by Hutton & Roderick (1970) and Chapman (1975), and has been used to localize Ahd-1 in this region (Ahd-1 and Gpd-1 exhibit a recombination frequency of 10.3 ± 3.7 %) (Holmes, 1978b). The data from Table 3 is consistent with a gene order of Pgm-2 - Ahd-1 - Gpd-1. The recombination frequency data of Ahd-1 with Gpd-1, Pgm-2 and b also supports the proposal that Ahd-1 is localized between Pgm-2 and Gpd-1 (Tables 2 and 3; Holmes, 1978b). Recent metabolic studies have indicated that mitochondria1 aldehyde dehydrogenase (AHD) plays a very important role in the metabolism of acetaldehyde derived from ethanol, ensuring a low concentration of acetaldehyde in the blood leaving the liver (Grunnet, 1973; Parilla et al., 1974; Corral1 et al., 1976). Moreover, genetic variation of this isozyme in human livers has been recently reported (Harada et al., 1978), and this polymorphism has been proposed as the molecular basis for individual and racial differences in alcohol sensitivity (Goedde et al., 1979). Consequently, genetic analyses of mitochondria1 AHD are of particular significance to studies on the genetic control of alcohol metabolism in mammals. In summary, this report confirms previous studies which demonstrated that the genetic locus encoding mitochondrial aldehyde dehydrogenase in the mouse (Ahd-1) is on chromosome 4 (Holmes, 1978b), and positions the gene with respect to b (brown), Pgrn-2 (encoding phosphoglucomutase B) and Gpd-1 (encoding the liver and kidney isozyme of hexose-6-phosphate dehydrogenase). In addition, the distribution of the 2-allelic phenotypes for this isozyme has been examined among 43 in- bred strains of mice.     

Isoelectric focusing studies of aldehyde dehydrogenases, alcohol dehydrogenases and oxidases from mammalian anterior eye tissues

1. Isoelectric focusing (IEF) and zymogram methods were used to examine the tissue distribution, multiplicity and substrate specificities of alcohol dehydrogenases (ADHs), aldehyde dehydrogenases (ALDHs) and ocular oxidases (EOXs) from mammalian anterior eye tissues. 2. Baboon, cattle, pig and sheep corneal extracts exhibited high ALDH activities; the corneal ALDHs were distinct from the major liver ALDHs and distinguished by their preference for medium-chain aldehydes. 3. Baboon and pig corneal extracts also showed high ADH activities, by comparison with ovine and bovine samples. Moreover, the ADHs were distinct from the major liver isozymes in pI value and substrate specificity. 4. Mammalian lens extracts exhibited significant ALDH activity of a form corresponding to the major liver cytosolic isozyme. Minor activity of the corneal enzyme was also observed in some species. 5. Lens ADH phenotypes were species-specific, and consisted of either Class II activity (baboon and sheep), Class III ADH activity (pig), or activities of both ADH classes (cattle). 6. Lens extracts also exhibited a complex pattern of ocular oxidase (EOX) activities following IEF. 7. A role in peroxidatic aldehyde detoxification is proposed for these enzymes in anterior eye tissues.     

Mouse mitochondrial aldehyde dehydrogenase isozymes: purification and molecular properties

Aldehyde dehydrogenase isozymes (AHD-1 and AHD-5) have been isolated in a highly purified state from extracts of mouse liver mitochondria. The enzymes have distinct subunit sizes, as determined by SDS/polyacrylamide gel electrophoresis: AHD-1, 63,000; AHD-5, 49,000. Gel exclusion chromatography, using sephadex G-200, indicated that both isozymes are dimers, although AHD-1 may also exist as a monomeric form as well. The enzymes exhibited widely divergent kinetic characteristics. The purified allelic forms of AHD-1, AHD-1A (C57BL/6J mice) and AHD-1B (CBA/H mice), exhibited high Km values with acetaldehyde as substrate, 1.4 mM and 0.78 mM respectively, whereas AHD-5 exhibited a low Km value with acetaldehyde of 0.2 microM. In addition, the isozymes exhibited distinct pH optima for catalysis (AHD-1, pH range 6.5-7.5; AHD-5, pH range 8.5-10.0), and were differentially sensitive towards disulphuram inhibition, with 50% inhibition occurring 13 and 0.1 microM for the AHD-1 and AHD-5 isozyme respectively. Based upon the kinetic characteristics, it is suggested that AHD-5 may be the primary enzyme for oxidizing mitochondrial acetaldehyde during ethanol oxidation in vivo.     

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.     

Liver cytosolic aldehyde dehydrogenases from "alcohol-drinking" and "alcohol-avoiding" mouse strains: purification and molecular properties

Liver cytosolic aldehyde dehydrogenases (AHD-2) have been isolated in a highly purified state from "alcohol-drinking" (C57BL/6J) and "alcohol-avoiding" (DBA/2J) strains of mice. The purified enzymes were resolved into three major and one minor form of activity by isoelectric focusing (IEF) techniques and showed similar zymogram patterns. The enzymes had identical subunit sizes on SDS-polyacrylamide gels: 53,000. Gel exclusion chromatography, using Ultrogel AcA34, indicated that the enzymes were dimers. The enzymes exhibited biphasic kinetic characteristics and were readily distinguished from each other. The purified forms of AHD-2 from C57BL/6J and DBA/2J mice exhibited two apparent Km values in each case: 10 microM/100 microM and 30 microM/330 microM respectively. AHD-2 exhibited a broad pH optimum in the range 7.0-9.0 and was very sensitive towards disulphuram inhibition, with 50% inhibition occurring at 0.17 microM. The kinetic results support proposals that AHD-2 may be the primary enzyme for oxidizing acetaldehyde during ethanol oxidation in vivo.     

Gene markers for alcohol-metabolizing enzymes among recombinant inbred strains of mice with differential behavioural responses towards alcohol

The genetic variability of alcohol dehydrogenase (C2 isozyme), aldehyde dehydrogenase (A2 isozyme) and aldehyde oxidase (A2 isozyme) has been examined among recombinant inbred strains of mice which have been previously studied concerning their differential behavioural responses towards alcohol. The results showed no correlation between biochemical phenotype for these loci and behavioural response.     

Aldehyde reductase isozymes in the mouse: Evidence for two new loci and localization of Ahr-3 on chromosome 7

Evidence is presented for two new forms of mouse liver and kidney aldehyde reductase activity (designated AHR-3 and AHR-4) resolved using cellulose acetate electrophoresis zymogram techniques and stained by glyceraldehyde and NADPH as substrate and coenzyme, respectively. Activity variants were observed for those isozymes among inbred strains of mice and used in a genetic analyses to support a proposal for two new genetic loci (Ahr-3 and Ah-4) which control the activity phenotype for these isozymes. Segregation analysis indicated that these loci are separately localized on the mouse genome, with Ahr-3 positioned on the distal end of chromosome 7. Liver AHR-2 (or hexonate dehydrogenase) exhibited no detectable phenotypic variation among the 44 inbred strains of mice examined. The AHR-3 and AHR-4 isozymes were readily distinguished from AHR-1 [or aldehyde reductase A₂, described previously by Duley and Holmes (Biochem. Genet. 20:1067, 1982)], hexonate dehydrogenase (AHR-2), and alcohol dehydrogenase A₂ in terms of their differential substrate, coenzyme, and inhibitor specificities.     

Gene markers for alcohol-metabolizing enzymes among recombinant inbred strains of mice with differential behavioural responses towards alcohol

The genetic variability of alcohol dehydrogenase (C₂ isozyme), aldehyde dehydrogenase (A₂ isozyme) and aldehyde oxidase (A₂ isozyme) has been examined among recombinant inbred strains of mice which have been previously studied concerning their differential behavioural responses towards alcohol. The results showed no correlation between biochemical phenotype for these loci and behavioural response.     

Acid phosphatases of the mosquito Culex tarsalis coquillett

1. Spectrophotometric and isoelectric focusing (IEF) electrophoretic characterization of the acid phosphatases (ACP) of the mosquito, Culex tarsalis, are presented. 2. ACP hydrolysis of P-nitrophenylphosphate (Pnp) was optimal at 37 degrees C, pH 5.25 in the presence of 15 mM MgCl2 and 0.1% (w/v) polyvinylpyrollidone (PVP). Vmax and Km values varied significantly between the various mosquito strains examined. 3. Several divalent cations (i.e. Mn2+, Ca2+, Ba2+ and Co2+), either the chloride or sulphate salts, were stimulatory for ACP. Both Cu2+ and Fe2+ (15 mM) were inhibitory. 4. Slight inhibition (i.e. 10%) of ACP activity was observed with dithiothreitol (100 mM) and 50% inhibition by cysteine (100 mM). 5. ACP activity was cyclic during the 15-day post-adult emergence period of the study. No significant differences were noted between the ACP specific activities of males and females nor between geographic strains. 6. IEF electrophoresis revealed three alpha-naphthyl phosphate hydrolytic ACP isozymes within the pH 4.5-5.5 range (i.e. ACP4.8, ACP5.3 and ACP5.5). 7. IEF ACP isozymes were stimulated by PVP, Mg2+, Zn2+ and inhibited by cysteine, EDTA (except ACP5.3) and NaFl. 8. IEF detection of ACP with Pnp revealed an ACP isozyme (ACP4.3) distinct from those ACP isozymes capable of alpha-naphthyl phosphate hydrolysis.     

Genetics,ontogeny, and testosterone inducibility of aldehyde oxidase isozymes in the mouse: Evidence for two genetic loci (Aox-1 and Aox-2) closely linked on chromosome 1

Null-activity and low-activity variants for the liver supernatant isozymes of aldehyde oxidase (designated AOX-1 and AOX-2) were observed in inbred strains and in Harwell linkage testing stocks of Mus musculus. The genetic loci determining the activity of these isozymes (designated Aox-1 and Aox-2, respectively) are closely linked on chromosome 1 near Id-1 (encoding the soluble isozyme of isocitrate dehydrogenase). Linkage data of Aox-1 with Id-1 and Dip-1 (encoding a kidney peptidase) demonstrated that this gene coincides with or is closely linked to Aox (Watson et al., 1972). Ontogenetic analyses demonstrated that liver AOX-1 appeared just before birth and increased in activity during postnatal development, whereas liver AOX-2 was observed only during postnatal development. Adult male livers exhibited higher AOX-1 and AOX-2 activities than adult female livers. Both isozymes were significantly reduced in activity by castration of adult males and increased following testosterone administration to castrated males and normal female mice.     

Genetics and development of ocular oxidases in the mouse: evidence for a new locus (Eox-l) closely linked with the aldehyde oxidase loci on chromosome 1

Summary. Isoelectric focusing (IEF) and histochemical techniques were used to examine the genetics, postnatal development and biochemical properties of ocular oxidases (EOXs) among inbred strains of mice. The designation as EOX was made on a provisional basis, since the 'natural' substrate(s) for this enzyme have not been identified. Five major forms were resolved from adult animals, which exhibited high activity in murine lens and low activity in the cornea. An additional ocular oxidase was observed in neonatal animals. Genetic analyses demonstrated that one of these enzymes (EOX-1) is encoded by a locus (Eox-1) which is closely linked with, but distinct from, the aldehyde oxidase (Aox) gene complex on chromosome one of the mouse. These results support the proposal that ocular oxidases are distinct from the major liver AOXs in this organism.     

Analysis of neuraminidase isozyme phenotypes in mammalian tissues: an electrophoretic approach

A simple cellulose acetate electrophoretic method for visualizing mammalian neuraminidase isozymes has been developed. Application of the method with rat and mouse liver extracts reveals the presence of two distinct isozymes in each species. Each isozyme exhibits tremendous variation in activity between inbred strains. The two isozymes vary independently of one another suggesting that their activities are controlled by different genes. The neuraminidase phenotypes detected in these inbred strains via electrophoresis are consistent with published accounts of neuraminidase phenotypes determined fluorometrically in whole liver homogenates, but also indicate the presence of a second isozyme not perceived by this other procedure.     

Aldehyde dehydrogenase (ALDH) isozymes in the gray short-tailed opossum (Monodelphis domestica): Tissue and subcellular distribution and biochemical genetics of ALDH3

Polyacrylamide gel isoelectric focusing (PAGE-IEF), cellulose acetate electrophoresis, and histochemical techniques were used to examine the tissue and subcellular distribution, genetics and biochemical properties of aldehyde dehydrogenase (ALDH) isozymes in a didelphid marsupial, the gray short-tail opossum (Monodelphis domestica). At least 14 zones of activity were resolved by PAGE-IEF and divided into five isozyme groups and three ALDH classes, based upon comparisons with properties previously reported for human, baboon, rat, and mouse ALDHs. Opossum liver ALDHs were distributed among cytosol (ALDHs 1 and 5) and large granular (mitochondrial) fractions (ALDHs 2 and 5). Similarly, kidney ALDHs were distributed between the cytosol (ALDH5) and the mitochondrial fractions (ALDHs 2, 4, and 5), whereas a major isozyme (ALDH3), found in high activity in cornea, esophagus, ear pinna, tail, and stomach extracts, was localized predominantly in the cytosol fraction. Phenotypic variants of the latter enzyme were shown to be inherited in a normal Mendelian fashion, with two alleles at a single locus (ALDH3) showing codominant expression. The data provided evidence for genetic identity of corneal, ear pinna, tail, and stomach ALDH3 and supported biochemical evidence from other mammalian species that this enzyme has a dimeric subunit structure.     

Molecular basis of the isozymes of bovine glucose-6-phosphate isomerase

Glucose-6-phosphate isomerase occurs in different bovine tissues as multiple, catalytically active isozymes which can be resolved by polyacrylamide gel electrophoresis (PAGE) and isoelectric focusing (IEF). Most differentiated tissues have five distinct forms with apparent pI values of 7.2, 7.0, 6.8, 6.6, and 6.4. Young, mitotically active, cells of the intestinal mucosa and the epithelium of the eye lens show only the two more basic isozymes, while old cells in the cortex and nucleus of the eye lens accumulate the more acidic isozymes. All of the isozymes exhibit equal separation based on charge-to-mass ratio (PAGE) and charge (IEF), thus indicating only charge changes. The isozyme patterns are unchanged in the presence of reducing agents or protease inhibitors. Each isozyme was purified to homogeneity and shown to exhibit identical subunit molecular weights (59,000) on SDS-gel electrophoresis. Each of the isolated isozymes, when subjected to PAGE or IEF, exhibited a single band, indicating that the isozymes are not generated as a result of electrophoresis. When the most basic isozyme was incubated in vitro under mild alkaline conditions, there was a spontaneous generation of the more acidic isozymes with properties identical to those found in vivo. The isozymes, thus, appear to be the result of spontaneous, postsynthetic modifications involving the addition of equal numbers of negative charges and are consistent with the deamidation of specific asparagine and/or glutamine residues.     

Stomach and duodenal alcohol and aldehyde dehydrogenase isozymes in Chinese

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) isozyme phenotypes were determined in surgical and endoscopic biopsies of the stomach and duodenum by agarose isoelectric focusing. gamma-ADH was found to be the predominant form in the mucosal layer whereas beta-ADH was predominant in the muscular layer. Low-Km ALDH1 and ALDH2 were found in the stomach and duodenum. High-Km ALDH3 isozymes occurred only in the stomach but not in the duodenum. The isozyme patterns of gastric mucosal ALDH2 and ALDH3 remained unchanged in the fundus, corpus, and antrum. The stomach ALDH3 isozymes exhibited a Km value for acetaldehyde of 75 mM, and an optimum for acetaldehyde oxidation at pH 8.5. Since the Km value was high, ALDH3 contributed very little, if any, to gastric ethanol metabolism. The activities of ALDH in the gastric mucosa deficient in ALDH2 were 60-70% of that of the ALDH2-active phenotypes. These results indicate that Chinese lacking ALDH2 activity may have a lower acetaldehyde oxidation rate in the stomach during alcohol consumption.