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 C57 BL/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 × 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.     

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.     

Inhibition of human brain aldose reductase and hexonate dehydrogenase by alrestatin and sorbinil

Abstract: Human brain aldose reductase and hexonate dehydrogenase are inhibited by alrestatin (AY 22,284) and sorbinil (CP 45,634). Inhibition by alrestatin is noncompetitive for both enzymes, and slightly stronger for hexonate dehydrogenase ( K _I values 52-250 μ M ) than for aldose reductase ( K _I values 170-320 μ M ). Sorbinil inhibits hexonate dehydrogenase far more potently than aldose reductase, K _I values being 5 μ M for hexonate dehydrogenase and 150 μ M for aldose reductase. The inhibition of hexonate dehydrogenase by sorbinil is noncompetitive with respect to both aldehyde and NADPH substrates, and is thus kinetically similar to the inhibition by alrestatin. However, sorbinil inhibition of aldose reductase is uncompetitive with respect to glyceraldehyde and noncompetitive with NADPH as the varied substrate. Inhibition of human brain aldose reductase by these two inhibitors is much less potent than that reported for the enzyme from other sources.     

Interrelationships among human aldo-keto reductase: immunochemical, kinetic and structural properties

We have propsed earlier a three gene loci model to explain the expression of the aldo-keto reductases in human tissues. According to this model, aldose reductase is a monomer of α subunits, aldehyde reductase I is a dimer of α, β subunits, and aldehyde reductase II is a monomer of δ subunits. Using immunoaffinity methods, we have isolated the subunits of aldehyde reductase I (α and β) and characterized them by immunocompetition studies. It is observed that the two subunits of aldehyde reductase I are weakly held together in the holoenzyme and can be dissociated under high ionic conditions. Aldose reductase (α subunits) was generated from human placenta and liver aldehyde reductase I by ammonium sulfate (80% saturation). The kinetic, structural and immunological properties of the generated aldose reductase are similar to the aldose reductase obtained from the human erythrocytes and bovine lens. The main characteristic of the generated enzyme is the requirement of Li₂SO₄(0.4 M) for the expression of maximum enzyme activity, and its K_m for glucose is less than 50 mM, whereas the parent enzyme, aldehyde reductase I, is completely inhibited by 0.4 M Li₂SO₄ and its K_m for glucose is more than 200 mM. The β subunits of aldehyde reductase I did not have enzyme activity but cross-reacted with anti-aldehyde reductase I antiserum. The β subunits hybridized with the α subunits of placenta aldehyde I, and aldose reductase purified from human brain and bovine lens. The hybridized enzyme had the characteristics properties of placenta aldehyde reductase I.     

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.     

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.     

Enzyme markers in inbred rat strains: Genetics of new markers and strain profiles

Twenty-six inbred strains of the laboratory rat (Rattus norvegicus) were examined for electrophoretic variation at an estimated 97 genetic loci. In addition to previously documented markers, variation was observed for the enzymes aconitase, aldehyde dehydrogenase, and alkaline phosphatase. The genetic basis of these markers (Acon-1, Ahd-2, and Akp-1) was confirmed. Linkage analysis between 35 pairwise comparisons revealed that the markers Fh-1 and Pep-3 are linked. The strain profiles of the 25 inbred strains at 11 electrophoretic markers are given.     

Asymmetric reduction of ethyl 4-chloro-3-oxobutanoate to ethyl (<Emphasis Type="Italic">R</Emphasis>)-4-chloro-3-hydroxybutanoate with two co-existing,recombinant<Emphasis Type="Italic"> Escherichia coli</Emphasis> strains

Two recombinant strains, E. coli M15 (pQE30-alr0307) and E. coli M15 (pQE30-gdh0310), which were constructed to express, respectively, an NADPH-dependent aldehyde reductase gene and a glucose dehydrogenase gene, were mixed in an appropriate ratio and used for the asymmetric reduction of ethyl 4-chloro-3-oxobutanoate to ethyl (R)-4-chloro-3-hydroxybutanoate. The former strain acted as catalyst and the latter functioned in NADPH regeneration. The biotransformation was completed effectively without any addition of glucose dehydrogenase or NADP⁺/NADPH. An optical purity of 99% (ee) was obtained and the product yield reached 90.5% from 28.5 mM substrate. Revisions requested 27 July 2004/23 September 2004; Revisions received 21 September 2004/29 November 2004     

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.     

Intracellular Localization and Characterization of Beef Liver Aldehyde Dehydrogenase Isozymes

Various physiological roles of mammalian aldehyde dehydrogenase had been anticipated because of its broad substrate specificity. In order to clarify roles of the enzyme and the regulation of aldehyde metabolisms in liver, the intracellular distribution and isozyme of beef liver aldehyde dehydrogenase were studied.

The presence of the mitochondrial, the microsomal and the cytoplasmic isozymes were proved by the isoelectric focusing. These isozymes were different from each other in pH-activity curve in the responces for steroid hormones and disulfiram.

It was suggested by comparing the reactivities of these isozymes for various aldehydes that particular aldehyde might be oxidized by a favorite isozyme at particular locality in the liver cells and that a share of physiological role among these isozymes is probable.     

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.     

The involvement of alcohol dehydrogenase and aldehyde dehydrogenase in alcohol/aldehyde metabolism in Drosophila melanogaster

In this study we have examined the roles of alcohol dehydrogenase, aldehyde oxidase, and aldehyde dehydrogenase in the adaptation of Drosophila melanogaster to alcohol environments. Fifteen strains were characterized for genetic variation at the above loci by protein electrophoresis. Levels of in vitro enzyme activity were also determined. The strains examined showed considerable variation in enzyme activity for all three gene-enzyme systems. Each enzyme was also characterized for coenzyme requirements, effect of inhibitors, subcellular location, and tissue specific expression. A subset of the strains was chosen to assess the physiological role of each gene-enzyme system in alcohol and aldehyde metabolism. These strains were characterized for both the ability to utilize alcohols and aldehydes as carbon sources as well as the capacity to detoxify such substrates. The results of the above analyses demonstrate the importance of both alcohol dehydrogenase and aldehyde dehydrogenase in the in vivo metabolism of alcohols and aldehydes.     

Two Distinct Pancreatic Amylase Genes Are Active in Ybr Mice

The genetic determinants of pancreatic amylase expression in YBR mice differ in two respects from those of other inbred strains. First, there are two nonallelic amylase isozymes present in YBR pancreas, while most mouse strains express a single pancreatic amylase protein. In addition, the in vivo rate of total pancreatic amylase synthesis is 50% of that in other strains. Both these traits are determined by genetic sites in the region of the Amy-2 locus on mouse chromosome 3. To determine the molecular basis for the presence of two isozymes in this strain, we have compared portions of their amino acid sequences. Two differences between isozymes A₁ and B₁ were identified among the 77 residues compared. This result demonstrates that two distinct amylase genes are expressed in YBR pancreas.     

Characterization of aldehyde dehydrogenase from HTC rat hepatoma cells

We have proposed developing rat hepatoma cell lines as an in vitro model for studying the regulation of changes in aldehyde dehydrogenase activity occurring duringhepatocarcinogenesis. Aldehyde dehydrogenase purified in a single step from HTC rat hepatoma cells is identical to the aldehyde dehydrogenase isolated from rat hepatocellular carcinomas. HTC aldehyde dehydrogenase is a 110 kDa dimer composed of 54-kDa subunits, prefers NADP⁺ as coenzyme, and preferentially oxidizes benzaldehyde-like aromatic aldehydes but not phenylacetaldehyde. The substrate and coenzyme specificity, effects of disulfiram, pH profile and isoelectric point of HTC aldehyde dehydrogenase are also identical to these same properties of the tumor aldehyde dehydrogenase. In immunodiffusions, both isozymes are recognized with complete identity by anti-HTC aldehyde dehydrogenase antibodies. Having established that HTC aldehyde dehydrogenase is very similar, if not identical, to the aldehyde dehydrogenase found in hepatocellular carcinomas, simplifies the development of molecular probes for examination of the regulation of tumor aldehyde dehydrogenase activity in vivo and in vitro.     

Kinetic evidence for human liver and stomach aldehyde dehydrogenase-3 representing an unique class of isozymes

Substrate and coenzyme specificities of human liver and stomach aldehyde dehydrogenase (ALDH) isozymes were compared by staining with various aldehydes including propionaldehyde, heptaldehyde, decaldehyde, 2-furaldehyde, succinic semialdehyde, and glutamic -semialdehyde and with NAD⁺ or NADP⁺ on agarose isoelectric focusing gels. ALDH3 isozyme was isolated from a liver via carboxymethyl-Sephadex and blue Sepharose chromatographies and its kinetic constants for various substrates and coenzymes were determined. Consistent with the previously proposed genetic model for human ALDH3 isozymes (Yinet al., Biochem. Genet. 26:343, 1988), a single liver form and multiple stomach forms exhibited similar kinetic properties, which were strikingly distinct from those of ALDH1, ALDH2, and ALDH4 (glutamic -semialdehyde dehydrogenase). A set of activity assays using various substrates, coenzymes, and an inhibitor to distinguish ALDH1, ALDH2, ALDH3, and ALDH4 is presented. As previously reported in ALDH1 and ALDH2, a higher catalytic efficiency (V _max/K _m) for oxidation of long-chain aliphatic aldehydes was found in ALDH3, suggesting that these enzymes have a hydrophobic barrel-shape substrate binding pocket. Since theK _m value for acetaldehyde for liver ALDH3, 83 mM, is very much higher than those of ALDH1 and ALDH2, ALDH3 thus represents an unique class of human ALDH isozymes and it appears not to be involved in ethanol metabolism.This work was supported by grants from the National Science Council and the Academia Sinica, Republic of China.     

Aldose and aldehyde reductases in human tissues

Immunochemical characterizations of aldose reductase and aldehyde reductases I and II, partially purified by DEAE-cellulose (DE-52) column chromatography from human tissues, were carried out by immunotitration, using antisera raised against the homogenous preparations of human and bovine lens aldose reductase and human placenta aldehyde reductase I and aldehyde reductase II. Anti-aldose reductase antiserum cross-reacted with aldehyde reductase I, anti-aldehyde reductase I antiserum cross-reacted with aldose reductase and anti-aldehyde reductase II antiserum precipitated aldehyde reductase II, but did not cross-react with aldose reductase or aldehyde reductase I from all the tissues examined. DE-52 elution profiles, substrate specificity and immunochemical characterization indicate that aldose reductase is present in human aorta, brain, erythrocyte and muscle; aldehyde reductase I is present in human kidney, liver and placenta; and aldehyde reductase II is present in human brain, erythrocyte, kidney, liver, lung and placenta. Monospecific anti-α and anti-β antisera were purified from placenta anti-aldehyde reductase I antiserum, using immunoaffinity techniques. Anti-α antiserum precipitated both aldehyde reductase I and aldose reductase, whereas anti-β antibodies cross-reacted with only aldehyde reductase I. Based on these studies, a three gene loci model is proposed to explain the genetic interrelationships among these enzymes. Aldose reductase is a monomer of α subunits, aldehyde reductase I is a dimer of α and β subunits and aldehyde reductase II is a monomer of δ subunits.     

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.     

Isoelectric focusing studies of aldehyde dehydrogenases from mouse tissues: variant phenotypes of liver, stomach and testis isozymes

Isoelectric focusing techniques (IEF) were used to examine the tissue distribution and genetic variability of aldehyde dehydrogenases (AHDs) from inbred strains of mice. Twelve zones of AHD activity were resolved which were differentially distributed between tissues. Liver extracts exhibited highest activity for most enzymes, with the exception of isozymes found in stomach (AHD-4) and testis (AHD-4 and AHD-6). Genetic variants for AHD-1 (liver mitochondrial isozyme) and AHD-4 (stomach isozyme) were examined from inbred strains and F1 hybrid animals. The results were consistent with dimeric subunit structures (designated as A2 and D2 isozymes respectively). IEF patterns for activity variants of testis-specific AHD-6 were identical, with 3-banded phenotypes being observed. pI values for the AHD forms as well as for aldehyde oxidase and xanthine oxidase isozymes, which stain in the absence of coenzyme, were reported.     

Genetic control of LDH isozymes in the house fly,Musca domestica

Electrophoretic variations in lactate dehydrogenase from adult whole body homogenates are described for three laboratory strains of house fly, Musca domestica. Several crosses between different electrophoretic forms provided evidence that the observed variations are due to segregation of alleles at two distinct loci (designated as A and B loci) and that the LDH isozymes of house flies are dimers formed by a random association of subunits controlled by the two loci.