The assay of uridine diphosphoglucose dehydrogenase activity: discrimination from xanthine dehydrogenase activity

The biochemical and quantitative cytochemical assays of the activity of uridine diphosphoglucose dehydrogenase (UDPG-D) have produced perplexing results. It is now shown that the perplexity may be due to the possibility that the coenzyme (NAD) required for UDPG-D activity, may be acting as a substrate for a second dehydrogenase, namely xanthine dehydrogenase, which may utilize NAD as its substrate. The activity of UDPG-D can be distinguished selectively by the pH of its optimal activity and by decreasing the concentration of the coenzyme used in the assay.     

An amperometric cellobiose dehydrogenase-based biosensor can be used for measurement of cellulase activity

The hemoflavoenzyme cellobiose dehydrogenase (CDH, EC 1.1.99.18) from Phanerochaete chrysosporium has been used in an amperometric redox polymer-based biosensor. Used in conjugation with a FIA system this biosensor can replace colorimetric assays for measuring cellobiose liberated from cellulose in a series of cellulase-containing samples. The biosensor gave the same result as the Somogyi-Nelson method in a less time-consuming and laborious manner. The two methods showed about the same precision.     

Assay of the pyruvate dehydrogenase complex by coupling with recombinant chicken liver arylamine N-acetyltransferase

The activity of the pyruvate dehydrogenase complex has long been determined in some laboratories by coupling the production of acetyl-coenzyme A (acetyl-CoA) to the acetylation of 4-aminoazobenzene-4'-sulfonic acid by arylamine N-acetyltransferase. The assay has some advantages, but its use has been limited by the need for large amounts of arylamine N-acetyltransferase. Here we report production of recombinant chicken liver arylamine N-acetyltransferase and optimization of its use in miniaturized assays for the pyruvate dehydrogenase complex and its kinase.     

Acetaldehyde dehydrogenase activity of the AdhE protein of Escherichia coli is inhibited by intermediates in ubiquinone synthesis

Defects in the acd gene (which may be allelic to ubiH) result in the inactivation of the coenzyme A-linked acetaldehyde dehydrogenase activity of the multifunctional AdhE protein of Escherichia coli. This activity is restored by addition of ubiquinone-0 to cell extracts. However, the alcohol dehydrogenase activity of the AdhE protein is not decreased by an acd mutation. Abolition of ubiquinone biosynthesis by mutation of ubiA or ubiF does not affect either the acetaldehyde dehydrogenase or the alcohol dehydrogenase activity of AdhE. Guaiacol (2-methoxyphenol), which resembles the intermediate that builds up in ubiH mutants, except in lacking the octaprenyl side-chain, was found to inhibit ethanol metabolism in vivo, presumably via inhibition of acetaldehyde dehydrogenase. In vitro assays confirmed that guaiacol inhibited acetaldehyde dehydrogenase. This suggests that the acetaldehyde dehydrogenase activity of AdhE is specifically inhibited by intermediates of ubiquinone synthesis that accumulate in acd mutants and that this inhibition may be relieved by ubiquinone.     

Kinetic and structural evidence for the identification of 11-hydroxythromboxane B2 dehydrogenase as cytosolic aldehyde dehydrogenase

We have recently purified 11-hydroxythromboxane B₂ dehydrogenase from porcine kidney and identified it as cytosolic aldehyde dehydrogenase (EC 1.2.1.3) based on amino acid analysis and other protein characteristics. In the present paper we have studied the catalytic interaction of thromboxane B₂ (TXB₂) with different aldehyde substrates and a potent aldehyde dehydrogenase inhibitor, disulfiram. TXB₂ was a competitive inhibitor of the aldehyde dehydrogenase reaction in assays with 3,4-dihydroxyphenylacetaldehyde, a high affinity substrate. The conversion of TXB₂ to 11-dehydro-TXB₂ was also inhibited by propanal and disulfiram.

The protein characteristics of the enzyme have also been further studied. The native enzyme is a tetramer and has an isoelectric point of 7.0 which is comparable with that of cytosolic aldehyde dehydrogenases from other species. Taken together the present data further indicate that 11-hydroxythromboxane B₂ dehydrogenase is identical with cytosolic aldehyde dehydrogenase and that substrates and inhibitors of aldehyde dehydrogenase interact with thromboxane metabolism in vitro.     

Application of Colorimetric Assays to Assess Viability, Growth and Metabolism of Hydrogel-Encapsulated Cells

The applicability of the colorimetric 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays to measure cell growth and viability in hydrogel encapsulation systems was investigated using HepG2 liver cells encapsulated in alginate matrices. The MTT assay was effective in measuring viable cell density in alginate-encapsulated cell systems, demonstrating less variance and higher throughput capability than hemocytometry. The LDH assay was effective in measuring dead cell density in monolayer cultures and in alginate-encapsulated cells simply by measuring the LDH concentration secreted into the medium. Further validation of these assays was shown in two additional cell lines (rat muscle and mouse embryonic fibroblasts). The MTT and LDH assays are particularly significant in the rapid evaluation of in vitro cell encapsulation device design.     

Determination of l-glutamate in various commercial soy sauce products using flow injection analysis with a modified electrode

A flow injection analysis (FIA) system with a modified electrode has been developed and optimized for determination of l-glutamate using l-glutamate oxidase (GLOD) (EC 1.4.3.11). GLOD was immobilized on controlled-pore glass using glutaraldehyde. The optimal potential applied on the working electrode was +700mV against a platinum (Pt) reference electrode. The optimal pH and flow rate of the carrier buffer were 7.4 and 1.5ml/min, respectively. A modified electrode was integrated into the FIA system in order to eliminate electroactive interference and it was used to determine l-glutamate in 39 samples of Thai commercial soy sauce products. The results obtained were compared with those obtained from enzymatic assay using glutamate dehydrogenase and those from a chromatographic assay using an amino acid analyser. Good correlations were observed amongst these methods. The results indicated that use of an FIA system with a modified electrode was able to eliminate electroactive interference and was applicable to the determination of l-glutamate in food samples. The modified FIA was faster and simpler than the more common methods of enzymatic and chromatographic analysis.     

Alcohol Dehydrogenases: Identification and Names for Gene Families

Plant gene products that have been described as `alcohol dehydrogenases' are surveyed and related to their CPGN nomenclature. Most are Zn-dependent medium chain dehydrogenases, including `classical' alcohol dehydrogenase (Adh1), glutathione-dependent formaldehyde dehydrogenase (Fdh1), cinnamyl alcohol dehydrogenase (Cad2), and benzyl alcohol dehydrogenase (Bad1). Plant gene products belonging to the short-chain dehydrogenase class should not be called alcohol dehydrogenases unless such activity is shown.     

Plagiorchis elegans: Histochemical localization of dehydrogenases in the cercarial stage

Cercariae of Plagiorchis elegans Rudolphi 1802 collected from experimentally infected snails, Lymnaea palustris, were subjected to various histochemical tests for dehydrogenase systems. A high degree of activity was demonstrated for succinic dehydrogenase (EC 1.3.99.1), malic dehydrogenase (EC 1.1.1.37), isocitric dehydrogenase (EC 1.1.1.41), α-glycerophosphate dehydrogenase (EC 1.1.1.8), and glucose 6-phosphate dehydrogenase (EC 1.1.1.49). These enzymes were present in the tegument, tail, caudal pocket, excretory bladder, acetabulum, and oral sucker, particularly in the muscles around the stylet. Only moderate activity was obtained for lactic dehydrogenase (EC 1.1.1.27) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44) at these sites, glutamic dehydrogenase (EC 1.4.1.2) was localized only in the tails of the cercariae and tests for alcohol dehydrogenase (EC 1.1.1.1) were completely negative. The cerebral ganglia and its commissures stained intensely in the tests for succinic, isocitric, α-glycerophosphate, and glucose 6-phosphate dehydrogenase systems. The results indicate the possibility that several energy-producing sequences may be available to these cercariae.     

Analysis of <Emphasis Type="Italic">ldh</Emphasis> genes in <Emphasis Type="Italic">Lactobacillus casei</Emphasis> BL23: role on lactic acid production

Lactobacillus casei is a lactic acid bacterium that produces L-lactate as the main product of sugar fermentation via L-lactate dehydrogenase (Ldh1) activity. In addition, small amounts of the D-lactate isomer are produced by the activity of a D-hydroxycaproate dehydrogenase (HicD). Ldh1 is the main L-lactate producing enzyme, but mutation of its gene does not eliminate L-lactate synthesis. A survey of the L. casei BL23 draft genome sequence revealed the presence of three additional genes encoding Ldh paralogs. In order to study the contribution of these genes to the global lactate production in this organism, individual, as well as double mutants (ldh1 ldh2, ldh1 ldh3, ldh1 ldh4 and ldh1 hicD) were constructed and lactic acid production was assessed in culture supernatants. ldh2, ldh3 and ldh4 genes play a minor role in lactate production, as their single mutation or a mutation in combination with an ldh1 deletion had a low impact on L-lactate synthesis. A Deltaldh1 mutant displayed an increased production of D-lactate, which was probably synthesized via the activity of HicD, as it was abolished in a Deltaldh1 hicD double mutant. Contrarily to HicD, no Ldh1, Ldh2, Ldh3 or Ldh4 activities could be detected by zymogram assays. In addition, these assays revealed the presence of extra bands exhibiting D-/L-lactate dehydrogenase activity, which could not be attributed to any of the described genes. These results suggest that L. casei BL23 possesses a complex enzymatic system able to reduce pyruvic to lactic acid.     

Comparison of mRNA Expression Levels Determined with TAQ–Man and Competitive Template RT–PCR

Two methods for measurement of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) mRNA expression were compared. Although the relative mRNA levels compared to β‐actin measured with competitive template RT–PCR were different from the data obtained with a TaqMan based PCR, a significant correlation between the two assays was found.     

Effect of Cadmium on Activities of Some Enzymes of Glycolysis and Pentose Phosphate Pathway in Pea

Activities of alcohol dehydrogenase, hexokinase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase were significantly inhibited by cadmium in germinating pea (Pisum sativum L. cv. Bonneville) seeds. The effect was concentration dependent in the range of 0.25 to 1.0 mM CdCl₂. The magnitude of detrimental effect on these enzymes was reduced during later stage of germination (9 d) largely because of fall in the activities of these enzymes in the control seeds germinated in water. In vitro, activities of hexokinase, glucose-6-phosphate dehydrogenase, and alcohol dehydrogenase were inhibited at 0.5 mM Cd²⁺ in the reaction mixture by 62, 67, and 36 %, respectively, however, 6-phosphogluconate dehydrogenase was insensitive to Cd²⁺. This revised version was published online in June 2006 with corrections to the Cover Date.     

Direct transfer of NADH from malate dehydrogenase to Complex I in Escherichia coli

During aerobic growth of Escherichia coli, nicotinamide adenine dinucleotide (NADH) can initiate electron transport at either of two sites: Complex I (NDH-1 or NADH: ubiquinone oxidoreductase) or a single-subunit NADH dehydrogenase (NDH-2). We report evidence for the specific coupling of malate dehydrogenase to Complex I. Membrane vesicles prepared from wild type cultures retain malate dehydrogenase and are capable of proton translocation driven by the addition of malate+NAD. This activity was inhibited by capsaicin, an inhibitor specific to Complex I, and it proceeded with deamino-NAD, a substrate utilized by Complex I, but not by NDH-2. The concentration of free NADH produced by membrane vesicles supplemented with malate+NAD was estimated to be 1 μM, while the rate of proton translocation due to Complex I was consistent with a some what higher concentration, suggesting a direct transfer mechanism. This interpretation was supported by competition assays in which inactive mutant forms of malate dehydrogenase were able to inhibit Complex I activity. These two lines of evidence indicate that the direct transfer of NADH from malate dehydrogenase to Complex I can occur in the E. coli system.     

Functional characterization of rat glutaryl-CoA dehydrogenase and its comparison with straight-chain acyl-CoA dehydrogenase

Glutaryl-CoA dehydrogenase catalyzes the oxidative decarboxylation of the γ-carboxylate of the substrate, glutaryl-CoA, to yield crotonyl-CoA and CO(2). The enzyme is a member of the acyl-CoA dehydrogenase (ACD) family of flavoproteins. In the present study, the catalytic properties of this enzyme, including its substrate specificity, isomerase activity, and interactions with inhibitors, were systematically studied. Our results indicated that the enzyme has its catalytic properties very similar to those of short-chain and medium-chain acyl-CoA dehydrogenase except its additional decarboxylation reaction. Therefore, the inhibitors of fatty acid oxidation targeting straight chain acyl-CoA dehydrogenase could also function as inhibitors for amino acid metabolism of lysine, hydroxylysine, and tryptophan.     

Alcohol dehydrogenase: multiplicity and relatedness in the solvent-producing clostridia

Abstract: Alcohol dehydrogenase (ADH) is a key enzyme for the production of butanol, ethanol, and isopropanol by the solvent-producing clostridia. Initial studies of ADH in extracts of several strains of Clostridium acetobutylicum and C. beijerinckii gave conflicting molecular properties. A more coherent picture has emerged because of the following results: (i) identification of ADHs with different coenzyme specificities in these species; (ii) discovery of structurally conserved ADHs (type 3) in three solvent-producing species; (iii) isolation of mutants with deficiencies in butanol production and restoration of butanol production with a cloned alcohol/aldehyde dehydrogenase gene; and (iv) resolution of various ' C. acetobutylicum ' cultures into four species. The three ADH isozymes of C. beijerinckii NRRL B592 have high sequence similarities to ADH-1 of Clostridium sp. NCP 262 (formerly C. acetobutylicum P262) and to the ADH domain of the alcohol/aldehyde dehydrogenase of C. acetobutylicum ATCC 824/DSM 792. The NADH-dependent activity of the ADHs from C. beijerinckii NRRL B592 and the BDHs from C. acetobutylicum ATCC 824 is profoundly affected by the pH of the assay, and the relative importance of NADH and NADPH to butanol production may be misappraised when NAD(P)H-dependent activities were measured at different pH values. The primary/secondary ADH of isopropanol-producing C. beijerinckii is a type-1 enzyme and is highly conserved in Thermoanaerobacter brockii (formerly Thermoanaerobium brockii ) and Entamoeba histolytica . Several solvent-forming enzymes (primary ADH, aldehyde dehydrogenase, and 3-hydroxybutyryl-CoA dehydrogenase) are very similar between C. beijerinckii and the species represented by Clostridium sp. NCP 262 and NRRL B643. The realization of such relationships will facilitate the elucidation of the roles of different ADHs because each type of ADH can now be studied in an organism most amenable to experimental manipulations.     

Mitochondriotropic action and DNA protection: Interactions between phenolic acids and enzymes

The protective action of caffeic (CA) and syringic (SA) acids on the genotoxicity exercised by snake venoms was investigated in this study. Molecular interactions between phenolic acids and the enzyme succinate dehydrogenase were also explored. In the electrophoresis assay, SA did not inhibit the genotoxicity induced by the venom. However, CA partially inhibited DNA degradation. In the comet assay, SA and CA exerted an inhibitory effect on the venom‐induced fragmentation. Succinate dehydrogenase presented, in computational analyzes, favorable energies to the molecular bond to both the malonic acid and the phenolic compounds evaluated. In the enzymatic activity assays, SA inhibited succinate dehydrogenase and interfered in the interaction of malonic acid. Meanwhile, CA potentiated the inhibition exerted by the malonic acid. The results suggest transient interactions between toxins present in venoms and phenolic acids, mainly by hydrogen interactions, which corroborate with the data from previous works.     

Development of a sensitive quantitative focal assay for human immunodeficiency virus infectivity.

Accurate and sensitive quantitation of infectious human immunodeficiency virus (HIV) has been difficult to achieve. In this report, a quantitative focal immunoassay (FIA) for HIV was developed using human HeLa cells rendered susceptible to HIV infection by introduction of the CD4 gene via a retrovirus vector. Infected cells were identified by using human anti-HIV antibodies or mouse monoclonal antibodies specific for HIV together with secondary fluorescein- or peroxidase-conjugated antibody specific for mouse or human immunoglobulins. The assay identified cells infected with either wild-type or culture-adapted HIV isolates and was capable of detecting 1 positive cell in 10(6) cells. The FIA was also effective at detecting cell-free HIV, and in contrast to assays using A3.01, CEM, and other human leukemia cells, the FIA detected most wild-type HIV isolates. HIV neutralization could be determined by using the FIA, and two monoclonal antibodies reactive with HIV gp120 were found to neutralize only the LAV-IIIB strain of HIV. These monoclonal antibodies, as well as antibodies in serum samples from patients with acquired immune deficiency syndrome, were able to inhibit the spread of HIV infection in human lymphocyte suspension cultures but not in CD4-positive HeLa cells growing attached to plastic dishes.     

NAD- and co-substrate (GSH or factor)-dependent formaldehyde dehydrogenases from methylotrophic microorganisms act as a class III alcohol dehydrogenase

Abstract The methylotrophic yeasts, Hansenula polymorpha and Candida boidinii , and the methylotrophic Gram-negative bacteria, Paracoccus denitrificans and Thiobacillus versutus (but not Methylophaga marina ), contain NAD/GSH-dependent formaldehyde dehydrogenase when grown on C₁-compounds. The enzymes appeared to be similar to each other and to the mammalian counterparts with respect to substrate specificity, including the ability to act as an alcohol dehydrogenase class III. The Gram-positive bacteria, Amycolatopsis methanolica and Rhodococcus erythropolis , possess NAD/Factor-dependent formaldehyde dehydrogenase when grown on C₁-compounds or on C₁-unit-containing substrates, respectively. These enzymes also exhibit alcohol dehydrogenase class III activity. Thus, like the mammalian ones, methylotrophic formaldehyde dehydrogenases show dual substrate specificity, suggesting that this is an inherent property of the enzyme.     

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 Iocus encoding liver L-α-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.     

Oxidative phosphorylation analysis: assessing the integrated functional activity of human skeletal muscle mitochondria—case studies

Oxidative phosphorylation analysis, performed on freshly-isolated mitochondria, assesses the integrated function of the electron transport chain (ETC) coupled to ATP synthesis, membrane transport, dehydrogenase activities, and the structural integrity of the mitochondria. In this review, a case study approach is employed to highlight detection of defects in the adenine nucleotide translocator, the pyruvate dehydrogenase complex, fumarase, coenzyme Q function, fatty acid metabolism, and mitochondrial membrane integrity. Our approach uses the substrates glutamate, pyruvate, 2-ketoglutarate (coupled with malonate), malate, and fatty acid substrates (palmitoylcarnitine, octanoylcarnitine, palmitoyl-CoA (with carnitine), octanoyl-CoA (with carnitine), octanoate and acetylcarnitine) in addition to succinate, durohydroquinone and TMPD/ascorbate to uncover metabolic defects that would not be apparent from ETC assays performed on detergent-solubilized mitochondria.