Fluorimetric detection of aldehyde dehydrogenase activity in human blood, saliva, and organ biopsies and kinetic differentiation between class I and class III isozymes

Unbalance between Pyridine Nucleotide Cofactors in The SOD1 Deficient Yeast Saccharomyces cerevisiae Causes Hypersensitivity to Alcohols and Aldehydes

Alcohol and aldehyde dehydrogenases are especially relevant enzymes involved in metabolic and detoxification reactions that occur in living cells. The comparison between the gene expression, protein content, and enzymatic activities of cytosolic alcohol and aldehyde dehydrogenases of the wild-type strain and the Δsod1 mutant lacking superoxide dismutase 1, which is hypersensitive to alcohols and aldehydes, shows that the activity of these enzymes is significantly higher in the Δsod1 mutant, but this is not a mere consequence of differences in the enzymatic protein content nor in the expression levels of genes. The analysis of the NAD(H) and NADP(H) content showed that the higher activity of alcohol and aldehyde dehydrogenases in the Δsod1 mutant could be a result of the increased availability of pyridine nucleotide cofactors. The higher level of NAD⁺ in the Δsod1 mutant is not related to the higher level of tryptophan; in turn, a higher generation of NADPH is associated with the upregulation of the pentose phosphate pathway. It is concluded that the increased sensitivity of the Δsod1 mutant to alcohols and aldehydes is not only a result of the disorder of redox homeostasis caused by the induction of oxidative stress but also a consequence of the unbalance between pyridine nucleotide cofactors.

Optical substrates for drug-metabolizing enzymes: Recent advances and future perspectives

Drug-metabolizing enzymes (DMEs), a diverse group of enzymes responsible for the metabolic elimination of drugs and other xenobiotics, have been recognized as the critical determinants to drug safety and efficacy. Deciphering and understanding the key roles of individual DMEs in drug metabolism and toxicity, as well as characterizing the interactions of central DMEs with xenobiotics require reliable, practical and highly specific tools for sensing the activities of these enzymes in biological systems. In the last few decades, the scientists have developed a variety of optical substrates for sensing human DMEs, parts of them have been successfully used for studying target enzyme(s) in tissue preparations and living systems. Herein, molecular design principals and recent advances in the development and applications of optical substrates for human DMEs have been reviewed systematically. Furthermore, the challenges and future perspectives in this field are also highlighted. The presented information offers a group of practical approaches and imaging tools for sensing DMEs activities in complex biological systems, which strongly facilitates high-throughput screening the modulators of target DMEs and studies on drug/herb‒drug interactions, as well as promotes the fundamental researches for exploring the relevance of DMEs to human diseases and drug treatment outcomes.

Enhancement in the Catalytic Activity of Human Salivary Aldehyde Dehydrogenase by Alliin from Garlic: Implications in Aldehyde Toxicity and Oral Health

BACKGROUND

Lower human salivary aldehyde dehydrogenase (hsALDH) activity increases the risk of aldehyde mediated pathogenesis including oral cancer. Alliin, the bioactive compound of garlic, exhibits many beneficial health effects.

OBJECTIVE

To study the effect of alliin on hsALDH activity.

METHODS

Enzyme kinetics was performed to study the effect of alliin on the activity of hsALDH. Different biophysical techniques were employed for structural and binding studies. Docking analysis was done to predict the binding region and the type of binding forces.

RESULTS

Alliin enhanced the dehydrogenase activity of the enzyme. It slightly reduced the Km and significantly enhanced the Vmax value. At 1 µM alliin concentration, the initial reaction rate increased by about two times. Further, it enhanced the hsALDH esterase activity. Biophysical studies indicated a strong complex formation between the enzyme and alliin (binding constant, Kb: 2.35 ± 0.14 x 103 M-1). It changes the secondary structure of hsALDH. Molecular docking study indicated that alliin interacts to the enzyme near the substrate binding region involving some active site residues that are evolutionary conserved. There was a slight increase in the nucleophilicity of active site cysteine in the presence of alliin. Ligand efficiency metrics values indicate that alliin is an efficient ligand for the enzyme.

CONCLUSION

Alliin activates the catalytic activity of the enzyme. Hence, consumption of alliincontaining garlic preparations or alliin supplements and use of alliin in pure form may lower aldehyde related pathogenesis including oral carcinogenesis.

The alterations in alcohol dehydrogenase and aldehyde dehydrogenase activities in the sera of patients with renal cell carcinoma

PURPOSE

In a previous study we showed that the total activity of alcohol dehydrogenase (ADH) and its isoenzyme class I was significantly higher in renal cancer (RCC) cells compared to normal kidney. The aim of this study was to compare the activities of ADH isoenzymes and aldehyde dehydrogenase (ALDH) in the sera of patients with different stages of RCC and healthy subjects.

MATERIALS AND METHODS

Serum samples were taken from 54 patients with clear cell RCC (17 patients in stage II, 22 in stage III and 15 in stage IV) and 52 healthy patients. Class III, IV of ADH and the total ADH activity was measured by the photometric method. For the measurement of ADH class I, II and the total ALDH activity we employed the fluorometric method.

RESULTS

The total activity of ADH and its isoenzyme class I were significantly higher in the sera of patients with every stage of RCC compared to healthy subjects. The analysis of ALDH activity did not indicate significant differences between tested groups.

CONCLUSIONS

The increased activity of total ADH and its isoenzyme class I in the sera of patients with RCC, seems to be caused by isoenzymes being released from cancerous cells and may be useful for diagnostics of renal cancer.

The Activity of Class I-IV Alcohol Dehydrogenase Isoenzymes and Aldehyde Dehydrogenase in Bladder Cancer Cells

OBJECTIVES

The aim of this study was to determine the differences in the activity of Alcohol Dehydrogenase (ADH) isoenzymes and Aldehyde Dehydrogenase (ALDH) in normal and cancerous bladder cells.

METHODS

Class III, IV of ADH and total ADH activity were measured by the photometric method and class I, II ADH and ALDH activity by the fluorometric method.

RESULTS

Significantly higher total activity of ADH was found in both, low-grade and high-grade bladder cancer, in comparison to healthy tissues.

CONCLUSION

The increased activity of total ADH in bladder cancer cells may be the cause of metabolic disorders in cancer cells, which may intensify carcinogenesis.

Activation of Human Salivary Aldehyde Dehydrogenase by Sulforaphane: Mechanism and Significance

Cruciferous vegetables contain the bio-active compound sulforaphane (SF) which has been reported to protect individuals against various diseases by a number of mechanisms, including activation of the phase II detoxification enzymes. In this study, we show that the extracts of five cruciferous vegetables that we commonly consume and SF activate human salivary aldehyde dehydrogenase (hsALDH), which is a very important detoxifying enzyme in the mouth. Maximum activation was observed at 1 μg/ml of cabbage extract with 2.6 fold increase in the activity. There was a ~1.9 fold increase in the activity of hsALDH at SF concentration of ≥ 100 nM. The concentration of SF at half the maximum response (EC₅₀ value) was determined to be 52 ± 2 nM. There was an increase in the V_max and a decrease in the K_m of the enzyme in the presence of SF. Hence, SF interacts with the enzyme and increases its affinity for the substrate. UV absorbance, fluorescence and CD studies revealed that SF binds to hsALDH and does not disrupt its native structure. SF binds with the enzyme with a binding constant of 1.23 x 10⁷ M^-1. There is one binding site on hsALDH for SF, and the thermodynamic parameters indicate the formation of a spontaneous strong complex between the two. Molecular docking analysis depicted that SF fits into the active site of ALDH3A1, and facilitates the catalytic mechanism of the enzyme. SF being an antioxidant, is very likely to protect the catalytic Cys 243 residue from oxidation, which leads to the increase in the catalytic efficiency and hence the activation of the enzyme. Further, hsALDH which is virtually inactive towards acetaldehyde exhibited significant activity towards it in the presence of SF. It is therefore very likely that consumption of large quantities of cruciferous vegetables or SF supplements, through their activating effect on hsALDH can protect individuals who are alcohol intolerant against acetaldehyde toxicity and also lower the risk of oral cancer development.

The diagnostic significance of serum alcohol dehydrogenase isoenzymes and aldehyde dehydrogenase activity in renal cell cancer patients

OBJECTIVES

In previous experiments, we have found an increased level of class I ADH and total ADH activity in RCC tissues. Changes in cancer cells may be reflected by ADH activity in the serum and could thus be helpful for diagnostics of renal cancer. The aim of this study was to investigate a potential role of ADH and ALDH as tumor markers for RCC.

MATERIAL AND METHODS

Serum samples were taken from 59 patients with RCC and 52 healthy subjects. Class III and IV of ADH and total ADH activity was measured by the photometric method. For measurement of class I and II ADH and ALDH activity, we employed the fluorometric method.

RESULTS

The total activity of ADH and ADH I was significantly higher in the serum of patients with every stage of RCC compared to healthy subjects. The diagnostics criteria was higher for ADH I than for total ADH activity. The diagnostic sensitivity for ADH I was 73.36%, specificity 85.61%, predictive values of positive and negative results were 79.12 and 75.03% respectively. Area under ROC curve for ADH I was 0.748 and for total ADH 0.689.

CONCLUSION

The results suggest a potential role of ADH I as a marker for RCC.

The activity of class I, II, III and IV alcohol dehydrogenase isoenzymes and aldehyde dehydrogenase in renal cell carcinoma

OBJECTIVES

Ethanol has been considered as a lifestyle risk factor for cancer in humans. While some studies have indicated that alcohol intake has a preventive effect for renal cell cancer, others have not. The metabolism of alcohol in cancer cells may be in many ways different than in healthy tissue and its disturbances could be associated with carcinogenesis. The aim of this study was to compare the metabolism of renal cell cancer cells and normal renal cells by measurement of ADH isoenzymes and ALDH activities in these tissues.

MATERIAL AND METHODS

The study material consisted of 43 cancerous renal tissues (14 patients in stage II, 19 in stage III and 10 in stage IV). Class III and IV ADH and total ADH activities were measured by the photometric method and class I and II ADH and ALDH activities by the fluorometric method with class-specific fluorogenic substrates.

RESULTS

The activity of the class I ADH isoenzyme and the total ADH was significantly higher in every stage of renal cell cancer as compared to healthy tissues. Analysis of ALDH activity did not show statistically significant differences between cancer and healthy cells.

CONCLUSION

The increased activity of total ADH in renal cell cancer, especially the class I isoenzyme and normal activity of ALDH, may be the factor intensifying carcinogenesis because of increasing the ability to highly carcinogenic acetaldehyde formation and causing disorders in metabolism of many biologically important substances.

The activity of class I, II, III and IV alcohol dehydrogenase isoenzymes and aldehyde dehydrogenase in ovarian cancer and ovarian cysts

PURPOSE

The metabolism of cancerous cells is in many ways different than in healthy cells. In ovarian cancer, cells exhibit activity of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), which participate in metabolism of many biological substances. The aim of this study was to compare the metabolism of ovarian cancer cells, ovarian cysts and normal ovarian cells by measurement of ADH isoenzymes and ALDH activities.

MATERIAL AND METHODS

The study material consisted of 36 cancerous ovarian tissues. Class III, IV of ADH and total ADH activity was measured by the photometric method and class I, II ADH and ALDH activity by the fluorometric method with class-specific fluorogenic substrates.

RESULTS

The activity of the class I ADH isoenzyme and the total ADH was significantly higher in ovarian cancer as compared to ovarian cysts and healthy tissues but there are no significant differences between ovarian cysts and healthy cells. The other classes of ADH tested, did not show significant differences between activity of cancerous cells and healthy ovary.

CONCLUSION

The increased activity of total ADH in ovarian cancer, especially the class I isoenzyme and normal activity of ALDH, may be the factor for the disturbances in important biological substances metabolism and could increase the concentration of highly carcinogenic acetaldehyde.

Formation of active products of benzaldehyde dimethane sulfonate (NSC 281612, DMS612) in human blood and plasma and their activity against renal cell carcinoma lines

Benzaldehyde dimethane sulfonate (BEN, DMS612, NSC281612) is an alkylating agent with activity against renal cell carcinoma and is being evaluated clinically. To support clinical trials, we developed an LC-MS/MS assay to detect and quantitate BEN and its metabolites/decomposition products. We tested the stability and products of BEN and benzoic acid dimethane sulfonate (BA) in plasma, blood and five renal carcinoma cell lines in vitro. Further, we determined the IC(50) of BEN, BA and four of their products in these cell lines. Low temperature and pH stabilized the analytes, and utilizing this resulted in an accurate, precise and reproducible assay. The half-lives of BEN and BA added to plasma in vitro were 220 and 5 min, while the half-life of BEN in whole blood was 18 min. The generation and degradation of up to 12 analytes were monitored, and structures confirmed with available authentic standards. The IC(50) for BEN was 5- to 500-fold lower than that of any of its products, while the cellular metabolic activity toward BEN correlated with ALDH activity and IC(50) values. We detected six of the in vitro products and their respective glucuronides in murine plasma after dosing BEN. The information gained from these experiments will be instrumental in the evaluation of the pharmacology of BEN in ongoing human trials.

The activity of class I, II, III and IV alcohol dehydrogenase isoenzymes and aldehyde dehydrogenase in cervical cancer

OBJECTIVE

The aim of this study was to compare the metabolism of cervical cancer cells and normal cervical cells by measurement of ADH isoenzymes and ALDH activities.

METHODS

The study material consisted of 40 cancerous cervical tissues. Class III, IV of ADH and total ADH activity was measured by the photometric method and class I, II ADH and ALDH activity by the fluorometric method with class-specific fluorogenic substrates.

RESULTS

The activity of the class I ADH isoenzyme and the total ADH were significantly higher in cervical cancer as compared to healthy tissues. Class I of ADH and total ADH activity are significantly higher in every stage of cancer as compared to the control. There are no significant differences between planoepitheliale and adenocarcinoma.

CONCLUSION

The increased activity of total ADH in cervical cancer may be the cause of some metabolic disorders in cancer cells, which may intensify carcinogenesis in this organ.

The activity of class I, II, III, and IV alcohol dehydrogenase isoenzymes and aldehyde dehydrogenase in endometrial cancer

OBJECTIVE

The metabolism of cancerous cells is in many ways different than in healthy cells. In endometrial cancer, cells exhibit activity of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), which participate in the metabolism of many biological substances. The aim of this study was to compare the metabolism of endometrial cancer cells and normal endometrial cells by measurement of ADH isoenzymes and ALDH activities in these tissues.

METHODS

The study material consists of cancerous endometrial tissues obtained from 34 patients. Total ADH activity was measured using the photometric method and ALDH activity using the fluorometric method. For the measurement of class I and II ADH isoenzyme activity, we employed the fluorometric method, with class-specific fluorogenic substrates. The activity of class III and IV ADH was measured using the photometric method.

RESULTS

The activity of the class I ADH isoenzyme was significantly higher in the endometrial cancer tissues when compared with normal endometrial tissues. The other classes of ADH tested did not show significant differences between activity of cancerous cells and healthy endometrium. The activity of total ADH was also significantly higher in endometrial cancer.

CONCLUSION

The increased activity of total ADH in endometrial cancer, especially the class I isoenzyme and normal activity of ALDH, may be the cause of disorders in metabolic pathways that use these isoenzymes and could increase the concentration of acetaldehyde, which is cancerogenic substance.

Salivary aldehyde dehydrogenase: activity towards aromatic aldehydes and comparison with recombinant ALDH3A1

A series of aromatic aldehydes was examined as substrates for salivary aldehyde dehydrogenase (sALDH) and the recombinant ALDH3A1. Para-substituted benzaldehydes, cinnamic aldehyde and 2-naphthaldehydes were found to be excellent substrates, and kinetic parameters for both salivary and recombinant ALDH were nearly identical. It was demonstrated that for the fluorogenic naphthaldehydes the only produced reaction product after incubation in saliva is the carboxylate.

A fluorogenic aldehyde bearing a 1,2,3-triazole moiety for monitoring the progress of aldol reactions

We have developed a new type of fluorogenic aldehyde bearing a 1,2,3-triazole moiety that is useful for monitoring the progress of aldol reactions through an increase in fluorescence. Whereas 6-methoxy-2-naphthaldehyde was highly fluorescent, the fluorogenic aldehyde, 4-formylbenzene connected to the 6-methoxy-2-naphthyl group through a 1,2,3-triazole moiety, was essentially nonfluorescent in aqueous solutions. We suggest that the 4-formylphenyl group acts as a quencher to suppress the fluorescence of the 6-methoxy-2-naphthyltriazole moiety. The product of the aldol reaction of this aldehyde does not have a quenching moiety and showed more than 800-fold higher fluorescence than the aldehyde. Assay systems using the fluorogenic aldehyde were validated by screening of aldol catalysts, ranking of the activities of the catalysts, and evaluation of reaction conditions.

Partially irreversible inactivation of mitochondrial aldehyde dehydrogenase by nitroglycerin

Mitochondrial aldehyde dehydrogenase (ALDH2) may be involved in the biotransformation of glyceryl trinitrate (GTN), and the inactivation of ALDH2 by GTN may contribute to the phenomenon of nitrate tolerance. We studied the GTN-induced inactivation of ALDH2 by UV/visible absorption spectroscopy. Dehydrogenation of acetaldehyde and hydrolysis of p-nitrophenylacetate (p-NPA) were both inhibited by GTN. The rate of inhibition increased with the GTN concentration and decreased with the substrate concentration, indicative of competition between GTN and the substrates. Inactivation of p-NPA hydrolysis was greatly enhanced in the presence of NAD⁺, and, to a lesser extent, in the presence of NADH. In the presence of dithiothreitol (DTT) inactivation of ALDH2 was much slower. Dihydrolipoic acid (LPA-H₂) was less effective than DTT, whereas glutathione, cysteine, and ascorbate did not protect against inactivation. When DTT was added after complete inactivation, dehydrogenase reactivation was quite modest (≤16%). The restored dehydrogenase activity correlated inversely with the GTN concentration but was hardly affected by the concentrations of acetaldehyde or DTT. Partial reactivation of dehydrogenation was also accomplished by LPA-H₂ but not by GSH. We conclude that, in addition to the previously documented reversible inhibition by GTN that can be ascribed to the oxidation of the active site thiol, there is an irreversible component to ALDH inactivation. Importantly, ALDH2-catalyzed GTN reduction was partly inactivated by preincubation with GTN, suggesting that the inactivation of GTN reduction is also partly irreversible. These observations are consistent with a significant role for irreversible inactivation of ALDH2 in the development of nitrate tolerance.

Free radicals and antioxidants in inflammatory processes and ischemia-reperfusion injury

This article discusses the current understanding of the role of free radicals and antioxidants in inflammatory processes and in ischemia reperfusion injury. It begins by describing the manifestations of acute inflammation and outlining the cellular events that occur during inflammation. It then describes the biochemical mediators of inflammation with special attention to nitric oxide. It details the process of hypoxia reperfusion injury, the enzymes involved, its treatment, and studies involving specific hypoxia reperfusion injuries in various animal species.

4-pyridone-3-carboxamide ribonucleoside triphosphate accumulating in erythrocytes in end stage renal failure originates from tryptophan metabolism

We recently identified an erythrocyte nucleotide accumulating in end-stage renal disease as 4-pyridone-3-carboxamide ribonucleotide triphosphate (4PYTP), a nucleotide never described previously. Plasma tryptophan concentration has been previously reported to be reduced in patients in chronic renal failure that is in turn associated with elevated precursors of tryptophan metabolism, including L -kynurenine and quinolinic acid, both of which have been implicated in the neurotoxic manifestations of chronic renal failure. Here we compare mean erythrocyte 4PYTP, and plasma tryptophan concentrations, in controls and four patient groups with renal impairment (10 per group) and confirmed a reduction in plasma tryptophan in patients on dialysis that corrected with renal transplantation. We found: An inverse correlation between plasma tryptophan and red cell 4PYTP concentrations (R(2)=0.44, P<0.001) when all patients were grouped together. Restoration of both tryptophan and 4PYTP concentrations to control values was only achieved following renal transplantation. 4PYTP was absent from erythrocytes in Molybdenum cofactor (MoCF) deficiency implicating aldehyde oxidase/dehydrogenase, a Molybdenum requiring enzyme. High 4PYTP erythrocyte concentrations in adenine or hypoxanthine-phosphoribosyltransferase deficient patients in severe uremia (113 microM and 103 microM), confirmed the lack of involvement of either enzyme in 4PYTP formation. We propose that 4PYTP is formed by a novel route involving the oxidation of the intermediates of NAD turnover from quinolinic acid by aldehyde oxidase.

Salivary aldehyde dehydrogenase--reversible oxidation of the enzyme and its inhibition by caffeine, investigated using fluorimetric method

OBJECTIVE

We have applied fluorimetric method to monitor aldehyde dehydrogenase (ALDH*) activity in human saliva samples to study inactivation, reactivation and inhibition of the enzyme.

DESIGN

Saliva samples were collected to buffer stock solution, containing various thiols, and assayed in the presence of the fluorogenic substrate 6-dimethylamino-2-naphthaldehyde and NAD(+). Fluorescence of the produced 6-dimethylamino-2-naphthalene carboxylate was used to measure the reaction rate.

RESULTS

Kinetic parameters for the highly fluorogenic substrate, 6-dimethylamino-2-naphthaldehyde were measured, with apparent K(m) of 7.9 microM at pH 7.3. The apparent K(m) for NAD(+) was 1.2 microM. The observed ALDH activity is unstable in the absence of thiols, but can be stabilized by 1mM glutathione, and inactivated enzyme can be re-activated within 10 min by treatment of 0.5 mM DTT. Two-assay procedure was applied to measure degree of inactivation of ALDH in saliva samples. It was found that degree of ALDH inactivation in fresh samples, stabilized by glutathione, is between 0% and 90%, with average value ca. 40%. Caffeine and theophylline were shown to be moderate inhibitors of salivary ALDH.

CONCLUSIONS

Oxidation of the salivary ALDH in fresh saliva may be reliably measured using fluorimetric two-assay procedure. Preliminary statistics indicate that in most individuals this enzyme is partially inactive. Inhibition of the salivary ALDH by caffeine may have consequences for nutrition safety.

Gender-related differences in hepatic activity of alcohol dehydrogenase isoenzymes and aldehyde dehydrogenase in humans

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), which are most abundant in the liver, are the main enzymes involved in ethanol metabolism in humans. Gender-related differences in total liver ADH and ALDH activity among different animal species have been observed in many studies. We measured total ADH and ALDH activity, and the activity of class I-IV ADH in the livers of male and female patients. Total ADH and class I and II ADH activities were significantly higher in males than in females (P=0.0052, P=0.0074, P=0.020, respectively). Class III and IV ADH and total ALDH activities were not significantly different between the genders (P=0.2917, P=0.0590, P=0.2940, respectively). The results of our study clearly show that there is a difference in enzymatic activity between male and female patients for those isoenzymes that actively participate in ethanol oxidation in the liver (class I and II ADH), although the main form of ADH in this organ is class III ADH.

Determination of Aldehyde Dehydrogenase (ALDH) Isozymes in Human Cancer Samples - Comparison of Kinetic and Immunochemical Assays

A fluorimetric assay of aldehyde dehydrogenase isozymes, based on naphthaldehyde oxidation, is compared with Western Blotting analysis on several clinical samples obtained from surgery. The comparison reveals qualitatively good correlation of ALDH1A1 isozyme detection with two methods and somewhat worse on ALDH3A1 assay.

Influence of human saliva on odorant concentrations. 2. aldehydes, alcohols, 3-alkyl-2-methoxypyrazines, methoxyphenols, and 3-hydroxy-4,5-dimethyl-2(5H)-furanone

The influence of human whole saliva on selected alcohols, aldehydes, 3-alkyl-2-methoxypyrazines, and phenols in food-relevant concentrations was investigated. At pH 7.5-8 it was found that the alcohols, methoxyphenols, methoxypyrazines, and 3-hydroxy-4,5-dimethyl-2(5H)-furanone remained unmodified by saliva, whereas aldehydes were reduced to their corresponding alcohols. Generally, the processes were found to be dependent on the salivary activity of the panelists as well as on the concentration of the applied odorants. Reduction of the aldehydes did not occur after thermal treatment of the saliva. These investigations are aimed at finding an explanation for longer lasting aftertaste in humans, as it is induced by some odor-active compounds after the consumption of food materials.

Alcohol and aldehyde dehydrogenase activity in the stomach and small intestine of rats poisoned with methanol

The activities of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) were measured with fluorogenic naphthaldehydes in the stomach and small intestine homogenates of rats dosed with 6 g methanol/kg bw after 6, 12, 24 h and 2, 5, 7 days. After intoxication with a sublethal dose, the ADH activity measured with these naphthaldehydes and ALDH activities in the stomach and small intestine were significantly decreased. This inhibition is stronger in the stomach and probably depends on cell damage and protein denaturation. We conclude that the activity measured with 6-methoxy-2-naphthaldehyde (MONAL-62) may be due to the activity of rat ADH-1 isoenzyme, and the activity detected with 4-methoxy-1-naphthaldehyde (MONAL-41) to the activity of rat ADH-2 isoenzyme.

Alcohol and aldehyde dehydrogenase activity measured with fluorogenic substrates in the liver of rats poisoned with methanol

The effect of methanol poisoning of rats on the hepatic activities of enzymes metabolizing alcohols was evaluated. The activities of alcohol (ADH) and aldehyde dehydrogenase (ALDH) in the liver of rats dosed with 1.5 and 3 g of methanol/kg b.w. were measured with new fluorogenic substrates (4-methoxy-1-naphthaldehyde [MONAL-41] for ADH and 6-methoxy-2-naphthaldehyde [MONAL-62] for ADH and ALDH) after 6, 12 and 24 hours and 2, 5 and 7 days. The methanol intoxication led to a dose dependent induction of ADH and ALDH activities. The higher dose of methanol induced the activities measured with both MONAL-41 and MONAL-62 with the peak on day 5; its effect was largest on the activity of ADH measured with MONAL-41. Only ADH activity measured with this substrate was induced by the lower dose of methanol during the whole time of the experiment; the activity of ADH measured with MONAL-62 and that of ALDH were induced only on day 1 of the intoxication. It is evident that sublethal methanol intoxication induces the hepatic activities of ADH and ALDH measured with fluorogenic substrates, and this induction depends on the dose of this alcohol.

An enantioselective fluorimetric assay for alcohol dehydrogenases using albumin-catalyzed beta-elimination of umbelliferone

3-hydroxybutyl umbelliferyl ethers (R)-1 and (S)-1 are fluorogenic substrates for alcohol dehydrogenases. Their oxidation forms ketone 2, which undergoes beta-elimination of umbelliferone under catalysis by bovine serum albumin, leading to a > 20-fold fluorescence increase at lambda em = 460 +/- 20 nm (lambda ex = 360 +/- 20 nm). Enantioselectivity is determined in two separate tests with each enantiomeric substrate.