Some properties of pig kidney-cortex aldehyde reductase.
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ABSTRACT:
SUBMITTER: Morpeth FF
PROVIDER: S-EPMC1162254 | biostudies-other | 1980 Nov
REPOSITORIES: biostudies-other
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Project description:Initial-rate measurements were made of the oxidations of pyridine-3-methanol and glycerol by NADP+ and of the reduction of the corresponding aldehydes by NADPH catalysed by pig kidney aldehyde reductase. In addition, a brief survey of the specificity of the enzyme towards aldehyde substrates and its sensitivity to the inhibitors ethacrynic acid, sodium barbitone and warfarin was made. The detailed kinetic work indicates a compulsory mechanism for aldehyde reduction, with NADPH binding before aldehyde. For alcohol oxidation, however, it is necessary to postulate the formation of kinetically significant amounts of binary complexes of the type enzyme-alcohol to explain the results. Thus, for alcohol oxidation random-order addition of substrates may occur. Inhibition studies of the kinetics of aldehyde reduction in the presence of the corresponding alcohol product provide further evidence for the existence of enzyme-alcohol complexes. Finally, detailed kinetic studies were made of the inhibition of pyridine-3-aldehyde reduction by sodium barbitone. The mechanism of the inhibition is discussed.
| S-EPMC1162630 | biostudies-other
Project description:An improved procedure for purifying aldehyde reductase is described. Utilization of Blue Dextran--Sepharose 4B and elimination of hydroxyapatite chromatography greatly improves the yield and ease of purification. Starting with 340 g of kidney tissue (two pig kidneys) approx. 50 mg of purified reductase may be routinely and reproducibly obtained. The purified reductase was used to establish the kinetic reaction mechanism of the enzyme. Initial-velocity analysis and product-inhibition data revealed that pig kidney aldehyde reductase follows an Ordered Bi Bi reaction mechanism in which NADPH binds first before D-glyceraldehyde. The limiting Michaelis constants for D-glyceraldehyde and NADPH were 4.8 +/- 0.7 mM and 9.1 +/- 2.1 micrometer respectively. The mechanism is similar to that of another monomeric oxidoreductase, octopine dehydrogenase, towards which aldehyde reductase exhibits several similarities, but differs from that of other aldehyde reductases. Phenobarbital is a potent inhibitor of aldehyde reductase, inhibiting both substrate and cofactor non-competitively (Ki = 80.4 +/- 10.5 micrometer and 66.9 +/- 1.6 micrometer respectively). Barbiturate inhibition seems to be a common property of NADPH-dependent aldehyde reductases.
| S-EPMC1186410 | biostudies-other
Project description:During the purification of pig kidney aldehyde reductase by an established procedure [Flynn, Cromlish & Davidson (1982) Methods Enzymol. 89, 501-506] a second enzyme with aldehyde reductase activity may be purified. When the procedure was performed in the presence of 5 mM-EDTA, only traces of the second reductase, pig kidney aldehyde reductase (minor form), were present. By the criterion of sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, pig kidney aldehyde reductase (minor form) had Mr 35 000, in comparison with Mr 40 200 found for pig kidney aldehyde reductase. Amino acid analysis of both enzymes and tryptic-peptide-map comparisons indicated differences in primary structure. The N-terminus of pig kidney aldehyde reductase (minor form) had the sequence Lys-Val-Leu, in contrast with the blocked (acetylated) N-terminus of pig kidney aldehyde reductase. The C-terminal sequence of both enzymes was the same. Both reductases were immunologically identical by double immunodiffusion and rocket immunoelectrophoresis. Pig kidney aldehyde reductase (minor form) had 50% of the specific activity of pig kidney aldehyde reductase when tested with a variety of aldehyde substrates. Michaelis constants of both enzymes for these substrates and for NADPH were similar, but values for kcat. and kcat./Km indicated that catalytically pig kidney aldehyde reductase was the more efficient enzyme. Typical aldehyde reductase inhibitors, such as phenobarbital and sodium valproate, had the same effect on both enzymes. It was concluded that pig kidney aldehyde reductase (minor form) is an enzymically active cleavage product of pig kidney aldehyde reductase which is formed when the latter is purified in the absence of the metalloproteinase inhibitor EDTA.
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Project description:The reduction of p-nitroso-N-dimethylaniline, p-nitroso-N-diethylaniline, p-nitrosophenol and p-nitroso-N-phenylaniline with NADPH in the presence of aldehyde reductases 1 and 2 is described. The reactivity of these nitroso substrates is increased by hydrophobic substituents and those promoting OH- elimination from the molecule of the reduced substrate. NN-Dimethylbenzoquinonedi-iminium cation was proved to be the reaction product formed from p-nitroso-N-dimethylaniline. The kinetics of the reduction of p-nitroso-N-dimethylaniline catalysed with aldehyde reductase 1 are rather complex at pH 7, and the preferred-pathway mechanism is probably involved. The reaction sequence approaches the ordered pattern at pH 8.5. It was shown that NADPH in equilibrium NADP+ recyclization proceeds in the presence of NADP+, p-nitroso-N-dimethylaniline, cyclohexanol and aldehyde reductase 1, the alcohol oxidation being the slowest step in this reaction. However, the rate of cyclohexanol oxidation surpasses that of the dissociation of NADPH from the enzyme.
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Project description:Oxidation of unsaturated phospholipids results in the generation of aldehyde side chains that remain esterified to the phospholipid backbone. Such "core" aldehydes elicit immune responses and promote inflammation. However, the biochemical mechanisms by which phospholipid aldehydes are metabolized or detoxified are not well understood. In the studies reported here, we examined whether aldose reductase (AR), which reduces hydrophobic aldehydes, metabolizes phospholipid aldehydes. Incubation with AR led to the reduction of 5-oxovaleroyl, 7-oxo-5-heptenoyl, 5-hydroxy-6-oxo-caproyl, and 5-hydroxy-8-oxo-6-octenoyl phospholipids generated upon oxidation of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PAPC). The enzyme also catalyzed the reduction of phospholipid aldehydes generated from the oxidation of 1-alkyl, and 1-alkenyl analogs of PAPC, and 1-palmitoyl-2-arachidonoyl phosphatidic acid or phosphoglycerol. Aldose reductase catalyzed the reduction of chemically synthesized 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphatidylcholine (POVPC) with a K(m) of 10 mum. Addition of POVPC to the culture medium led to incorporation and reduction of the aldehyde in COS-7 and THP-1 cells. Reduction of POVPC in these cells was prevented by the AR inhibitors sorbinil and tolrestat and was increased in COS-7 cells overexpressing AR. Together, these observations suggest that AR may be a significant participant in the metabolism of several structurally diverse phospholipid aldehydes. This metabolism may be a critical regulator of the pro-inflammatory and immunogenic effects of oxidized phospholipids.
| S-EPMC3475326 | biostudies-literature
Project description:3-Deoxyglucosone reductase activity in the extracts of rat, pig and human livers was potently inhibited by aldehyde reductase inhibitors. The major species of 3-deoxyglucosone reductase purified from human and pig livers were biochemically and immunochemically identical with aldehyde reductase. The two enzymes and rat liver aldehyde reductase exhibited higher catalytic efficiency for 3-deoxyglucosone than for D-glucuronate, a representative substrate of aldehyde reductase.
| S-EPMC1151532 | biostudies-other
Project description:Advances in synthetic biology and metabolic engineering have enabled the construction of novel biological routes to valuable chemicals using suitable microbial hosts. Aldehydes serve as chemical feedstocks in the synthesis of rubbers, plastics, and other larger molecules. Microbial production of alkanes is dependent on the formation of a fatty aldehyde intermediate which is converted to an alkane by an aldehyde deformylating oxygenase (ADO). However, microbial hosts such as Escherichia coli are plagued by many highly active endogenous aldehyde reductases (ALRs) that convert aldehydes to alcohols, which greatly complicates strain engineering for aldehyde and alkane production. It has been shown that the endogenous ALR activity outcompetes the ADO enzyme for fatty aldehyde substrate. The large degree of ALR redundancy coupled with an incomplete database of ALRs represents a significant obstacle in engineering E. coli for either aldehyde or alkane production. In this study, we identified 44 ALR candidates encoded in the E. coli genome using bioinformatics tools, and undertook a comprehensive screening by measuring the ability of these enzymes to produce isobutanol. From the pool of 44 candidates, we found five new ALRs using this screening method (YahK, DkgA, GldA, YbbO, and YghA). Combined deletions of all 13 known ALRs resulted in a 90-99% reduction in endogenous ALR activity for a wide range of aldehyde substrates (C2-C12). Elucidation of the ALRs found in E. coli could guide one in reducing competing alcohol formation during alkane or aldehyde production.
| S-EPMC4411948 | biostudies-literature
Project description:Aldehyde reductase from ox kidney cytosol has been fractionated into four forms, two of which have been purified to apparent homogeneity. One of the minor forms is shown to be heterogenous on polyacrylamide-gel electrophoresis. The substrate specificities of the four forms using a variety of aldehydes and ketones are presented. The sensitivity of the various forms to inhibition by sodium valproate, sodium barbitone and various benzodiazepines has been determined. The relationship of these forms to the previously described hexonate dehydrogenase, aldose reductase and prostaglandin dehydrogenase is discussed.
| S-EPMC1158490 | biostudies-other
Project description:Dimeric and monomeric proteins containing dihydrodiol dehydrogenase and aldehyde reductase activities were purified from pig lens. The dimeric enzyme of Mr 65,000 specifically oxidized the trans-dihydrodiols of naphthalene and benzene with NADP+ as a strict cofactor, and reduced alpha-diketones, aromatic aldehydes and glyceraldehyde with NADPH as a cofactor. The monomeric enzyme of Mr 35,000, although identical with aldose reductase, oxidized the trans-dihydrodiol of naphthalene at a pH optimum of 7.6. These results suggest that the two enzymes are involved in the pathogenesis of naphthalene cataract.
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Project description:The activity of pyruvate dehydrogenase (PDH) kinase in the purified PDH complex from pig kidney is sensitive to changes in ionic strength. The enzyme has optimum activity within a small range of ionic strength (0.03-0.05 M). An increase in ionic strength from 0.04 M to 0.2 M lowers the activity of PDH kinase by 32% and decreases the Km for ATP from 25 microM to 10 microM. At constant ionic strength (0.15 M) the enzyme has optimum activity over a broad pH range (7.2-8.0). The PDH kinase is stimulated 2.2-fold by 20 mM-K+, whereas Na+ even at high concentration (80 mM) has no effect on the enzyme activity. The stimulation of PDH kinase by K+ is not dependent on pH and ionic strength. PDH kinase is inhibited by HPO4(2-) in the presence of K+, whereas HPO4(2-) has no effect on the activity of this enzyme in the absence of K+. HPO4(2-) at concentrations of 2 and 10 mM inhibits PDH kinase by 28% and 55% respectively. The magnitude of this inhibition is not dependent on the ATP/ADP ratio. Inhibition by HPO4(2-) in the concentration range 0-10 mM is non-competitive with respect to ATP, and becomes mixed-type at concentrations over 10 mM. The Ki for HPO4(2-) is 10 mM. When HPO4(2-) is replaced by SO4(2-), the same effects on the activity of PDH kinase are observed. PDH kinase is also inhibited by Cl-. In the presence of 80 mM-Cl- the PDH kinase is inhibited by 40%. The inhibition by Cl- is not dependent on K+. In conclusion, we postulate that changes in phosphate concentrations may play a significant role in the regulation of PDH kinase activity in vivo.
| S-EPMC1132021 | biostudies-other