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At least 19 recordsLinked to original sources
PubMed2001

Membrane-bound sugar alcohol dehydrogenase in acetic acid bacteria catalyzes L-ribulose formation and NAD-dependent ribitol dehydrogenase is independent of the oxidative fermentation.

To identify the enzyme responsible for pentitol oxidation by acetic acid bacteria, two different ribitol oxidizing enzymes, one in the cytosolic fraction of NAD(P)-dependent and the other in the membrane fraction of NAD(P)-independent enzymes, were examined with respect to oxidative fermentation. The cytoplasmic NAD-dependent ribitol dehydrogenase (EC 1.1.1.56) was crystallized from Gluconobacter suboxydans IFO 12528 and found to be an enzyme having 100 kDa of molecular mass and 5 s as the sedimentation constant, composed of four identical subunits of 25 kDa. The enzyme catalyzed a shuttle reversible oxidoreduction between ribitol and D-ribulose in the presence of NAD and NADH, respectively. Xylitol and L-arabitol were well oxidized by the enzyme with reaction rates comparable to ribitol oxidation. D-Ribulose, L-ribulose, and L-xylulose were well reduced by the enzyme in the presence of NADH as cosubstrates. The optimum pH of pentitol oxidation was found at alkaline pH such as 9.5-10.5 and ketopentose reduction was found at pH 6.0. NAD-Dependent ribitol dehydrogenase seemed to be specific to oxidoreduction between pentitols and ketopentoses and D-sorbitol and D-mannitol were not oxidized by this enzyme. However, no D-ribulose accumulation was observed outside the cells during the growth of the organism on ribitol. L-Ribulose was accumulated in the culture medium instead, as the direct oxidation product catalyzed by a membrane-bound NAD(P)-independent ribitol dehydrogenase. Thus, the physiological role of NAD-dependent ribitol dehydrogenase was accounted to catalyze ribitol oxidation to D-ribulose in cytoplasm, taking D-ribulose to the pentose phosphate pathway after being phosphorylated. L-Ribulose outside the cells would be incorporated into the cytoplasm in several ways when need for carbon and energy sources made it necessary to use L-ribulose for their survival. From a series of simple experiments, membrane-bound sugar alcohol dehydrogenase was concluded to be the enzyme responsible for L-ribulose production in oxidative fermentation by acetic acid bacteria.

Cell Membrane↗
PubMed1984

Extended superfamily of short alcohol-polyol-sugar dehydrogenases: structural similarities between glucose and ribitol dehydrogenases.

The recently determined primary structure of glucose dehydrogenase from Bacillus megaterium was scanned by computerized comparisons for similarities with known polyol and alcohol dehydrogenases. The results revealed a highly significant similarity between this glucose dehydrogenase and ribitol dehydrogenase from Klebsiella aerogenes. Sixty-one positions of the 262 in glucose dehydrogenase are identical between these two proteins (23% identity), fitting into a homology alignment for the complete polypeptide chains. The extent of similarity is equivalent to that between other highly divergent but clearly related dehydrogenases (two zinc-containing alcohol dehydrogenases, 25%; sorbitol and zinc-containing alcohol dehydrogenases, 25%; ribitol and non-zinc-containing alcohol dehydrogenases, 20%), and suggests an ancestral relationship between glucose and ribitol dehydrogenases from different bacteria . The similarities fit into a previously suggested evolutionary scheme comprising short and long alcohol and polyol dehydrogenases, and greatly extend the former group to one composed of non-zinc-containing alcohol-polyol-glucose dehydrogenases.

Alcohol Dehydrogenase↗
PubMed1965

METABOLISM OF PENTOSES AND PENTITOLS BY AEROBACTER AEROGENES. 3. PHYSICAL AND IMMUNOLOGICAL PROPERTIES OF PENITOL DEHYDROGENASES AND PENTULOKINASES.

Mortlock, R. P. (Michigan State University, East Lansing), D. D. Fossitt, D. H. Petering, and W. A. Wood. Metabolism of pentoses and pentitols by Aerobacter aerogenes. III. Physical and immunological properties of pentitol dehydrogenases and pentulokinases. J. Bacteriol. 89:129-135. 1965.-Four pentulokinases and three pentitol dehydrogenases were purified from Aerobacter aerogenes PRL-R3, and the properties of the enzymes within each family were compared. d-Ribulokinase was purified from cells grown on ribitol, d-arabitol, and xylitol, and from a mutant constitutive for ribitol dehydrogenase; d-xylulokinase, from cells grown on d-xylose and xylitol; l-ribulokinase, from cells grown on l-arabinose; and l-xylulokinase, after growth on l-xylose. Similarly, ribitol dehydrogenase was purified after growth on ribitol, d-arabinose, and xylitol, and from the ribitol dehydrogenase-constitutive mutant. d-Arabitol dehydrogenase was obtained after growth on d-arabitol or d-xylose, and xylitol dehydrogenase was obtained after growth on xylitol. Except for l-xylulokinase, which also had a different S(20) value, the pentulokinases had identical pH optima, K(m) for the ketopentose, and sedimentation constants, and fractionated identically by a number of procedures. These kinases could be distinguished only by their substrate and immunological specificity. Ribitol dehydrogenase and d-arabitol dehydrogenase could be distinguished by several properties, but the properties of xylitol dehydrogenase were always similar to ribitol dehydrogenase. In all cases, individual kinases or dehydrogenases produced by different inducers had identical properties. These data constitute evidence against multiple forms of the same enzyme being produced by different inducers and against the dehydrogenase family containing essentially identical proteins differing only at the active site. For the kinases, three of the four appear to differ only at the active site.

Antibodies↗
PubMed1964

METABOLISM OF PENTOSES AND PENTITOLS BY AEROBACTER AEROGENES. II. MECHANISM OF ACQUISITION OF KINASE, ISOMERASE, AND DEHYDROGENASE ACTIVITY.

Mortlock, R. P. (Michigan State University, East Lansing), and W. A. Wood. Metabolism of pentoses by Aerobacter aerogenes. II. Mechanism of acquisition of kinase, isomerase, and dehydrogenase activity. J. Bacteriol. 88:845-849. 1964.-Aerobacter aerogenes PRL-R3 possesses the genetic information to synthesize, in the presence of the appropriate inducer, at least three members of the family of ketopentokinases, two members of the family of pentitol dehydrogenases, and two members of the family of aldopentose isomerases. That is, d-xylulokinase, d-ribulokinase, l-ribulokinase, ribitol dehydrogenase, d-arabitol dehydrogenase, d-xylose (--> d-xylulose) isomerase, and l-arabinose (--> l-ribulose) isomerase activities were detectable within 4 hr after addition of inducer. The possibility that mutation and selection are involved in the formation of l-xylulokinase, l-arabitol dehydrogenase, d-arabinose (--> d-ribulose) isomerase and d-lyxose (--> d-xylulose) isomerase could not be eliminated, because 11 hr or more of incubation after the addition of inducer were required before the appearance of these enzyme activities. d-Xylulokinase activity was induced in less than 2 hr when d-xylose or d-arabitol were inducers, but 45 hr were required for the appearance of activity when xylitol was the inducer, and 83 hr were required when d-lyxose was the inducer. Likewise, the time required for induction of ribitol dehydrogenase was 2 hr for ribitol, 12 hr for d-arabinose, and 45 hr for xylitol. The time required for the appearance of enzyme activity correlated with the time required for the beginning of cell growth and substrate utilization.

Alcohols↗
PubMed1985

Production of D- and L-xylulose by mutants of Klebsiella pneumoniae and Erwinia uredovora.

D-Xylulose and L-xylulose were produced biologically by the oxidation of a corresponding pentitol. A Klebsiella pneumoniae mutant was constructed for the oxidation of D-arabitol to D-xylulose. This mutant constitutively synthesized the D-arabitol permease system and D-arabitol dehydrogenase but was unable to produce the D-xylulokinase of the D-arabitol pathway or the D-xylose isomerase and D-xylulokinase of the D-xylose pathway. An Erwinia uredovora mutant which constitutively synthesized a novel xylitol-4-dehydrogenase but could not synthesize L-xylulokinase was used for the oxidation of xylitol to L-xylulose. Washed cell suspensions of either mutant incubated with 0.5% pentitol would oxidize 60 to 65% of the pentitol to the corresponding ketopentose in 18 h and excrete the ketopentose into the medium. Ketopentoses were rapidly purified from the remaining pentitol by hydroxyl affinity chromatography.

Aldose-Ketose Isomerases↗
PubMed1987

Reduced anterograde and retrograde accumulation of axonally transported phosphofructokinase in streptozotocin-diabetic rats: effects of insulin and the aldose reductase inhibitor 'Statil'.

This study examined anterograde and retrograde accumulation of axonally transported 6-phosphofructokinase activity, proximal and distal to sciatic nerve constrictions, in rats with streptozotocin-induced diabetes of 4 weeks' duration. There were deficits in accumulation on both sides of the constriction in untreated diabetic rats (proximal accumulation 66% of controls, p less than 0.05; distal accumulation 32% of controls, p less than 0.01). There was also a reduction in the phosphofructokinase activity per unit length unconstricted sciatic nerve in the untreated diabetic rats (87% of controls, p less than 0.05). Treatment of an age-matched group of diabetic rats with twice-daily insulin prevented all the above changes. There were significant increases, over untreated diabetic rats, in phosphofructokinase activity accumulated at constrictions (p less than 0.01 for both proximal and distal) and in unconstricted nerve (p less than 0.05). Indeed the activities measured in insulin-treated diabetic rats were virtually identical to those of controls. Treatment of a third group of diabetic rats with the aldose reductase inhibitor 'Statil' prevented or attenuated accumulations of polyol pathway metabolites and prevented depletion of myo-inositol in the sciatic nerve. In spite of these indications of effective aldose reductase inhibition, the drug was without effect on the deficits in accumulation of activity at ligatures or unconstricted nerve levels of phosphofructokinase activity. We conclude that short-term experimental diabetes in rats induced defects in both anterograde and retrograde axonal transport of 6-phosphofructokinase activity. These defects were prevented by intensive insulin treatment but were resistant to an effective aldose reductase inhibitor, indicating a lack of involvement of polyol pathway flux in their pathogenesis.

Aldehyde Reductase↗
PubMed1985

Role of aldose reductase in the development of diabetes-associated complications.

The aldose reductase-initiated intracellular accumulation of polyols has been clearly shown to have a hyperosmotic effect on the lens of experimental animals. Similar localized osmotic changes resulting in the onset of pathology may also occur in the nerve, corneal epithelium, and retinal pericytes. Except for experimental diabetic cataracts, however, the exact mechanism by which aldose reductase is involved in these diabetes-associated complications remains to be clarified.

Aldehyde Reductase↗
PubMed1985

Binding of an aldose reductase inhibitor to renal glomeruli.

The aldose reductase inhibitor Sorbinil affects several membrane-associated complexes including Na/K-ATPase activity, transport processes, and impulse propagation. These considerations, coupled with the drug's aromatic nature, suggested the possibility of direct interaction with cell membranes. In the present study, binding of [3H]-Sorbinil to isolated glomeruli was demonstrated. Binding is dose-dependent and saturable, and can be inhibited by increasing concentrations of unlabeled Sorbinil. These results may help explain the compound's diverse effects on membrane-associated processes.

Aldehyde Reductase↗
PubMed1988

Statil-sensitive polyol formation in nerve of galactose-fed mice.

The sciatic nerve of diabetic C57BL/Ks mice did not accumulate either sorbitol or fructose despite elevated nerve glucose levels, nor did they show a depletion of free myo-inositol. Galactose feeding of both nondiabetic and diabetic mice for five days resulted in marked accumulations of dulcitol in nerve indicating polyol forming activity. Levels of myo-inositol showed small elevations in nerves of galactose-fed mice which reached significance when compared to diabetic mice fed the standard diet. Dulcitol accumulation was prevented by concurrent administration of the aldose reductase inhibitor Statil, but this did not prevent the increased levels of myo-inositol.

Aldehyde Reductase↗
PubMed1990

Augmented polyol pathway activity and retinal pigment epithelial permeability in the diabetic BB rat.

In the present study we investigated the relationship between an augmented polyol pathway and the breakdown of the blood-retinal barrier in the spontaneously diabetic BB rat. Permeability experiments were performed in diabetic and age-matched non-diabetic BB rats in a longitudinal fashion using horseradish peroxidase. Increased permeability of horseradish peroxidase across the retinal pigment epithelium was noted after 6 months of diabetes. Abnormalities of the basal plasmalemmal infoldings of the retinal pigment epithelium were noted in the control animals and appeared to be exaggerated in diabetic rats. Simultaneous quantitative ultrastructural immunohistochemistry, using an affinity purified anti-BB rat aldose reductase antibody and protein-A gold, revealed a significant increase in the aldose reductase immunoreactivity of the retinal pigment epithelium in diabetic animals. These findings suggest that an augmented polyol pathway activity may play a role in the pathogenesis of the blood-retinal barrier breakdown at the level of the retinal pigment epithelium in the diabetic BB rat.

Aldehyde Reductase↗
PubMed2004

A novel NADH-linked l-xylulose reductase in the l-arabinose catabolic pathway of yeast.

An NADH-dependent l-xylulose reductase and the corresponding gene were identified from the yeast Ambrosiozyma monospora. The enzyme is part of the yeast pathway for l-arabinose catabolism. A fungal pathway for l-arabinose utilization has been described previously for molds. In this pathway l-arabinose is sequentially converted to l-arabinitol, l-xylulose, xylitol, and d-xylulose and enters the pentose phosphate pathway as d-xylulose 5-phosphate. In molds the reductions are NADPH-linked, and the oxidations are NAD(+)-linked. Here we show that in A. monospora the pathway is similar, i.e. it has the same two reduction and two oxidation reactions, but the reduction by l-xylulose reductase is not performed by a strictly NADPH-dependent enzyme as in molds but by a strictly NADH-dependent enzyme. The ALX1 gene encoding the NADH-dependent l-xylulose reductase is strongly expressed during growth on l-arabinose as shown by Northern analysis. The gene was functionally overexpressed in Saccharomyces cerevisiae and the purified His-tagged protein characterized. The reversible enzyme converts l-xylulose to xylitol. It also converts d-ribulose to d-arabinitol but has no activity with l-arabinitol or adonitol, i.e. it is specific for sugar alcohols where, in a Fischer projection, the hydroxyl group of the C-2 is in the l-configuration and the hydroxyl group of C-3 is in the d-configuration. It also has no activity with C-6 sugars or sugar alcohols. The K(m) values for l-xylulose and d-ribulose are 9.6 and 4.7 mm, respectively. To our knowledge this is the first report of an NADH-linked l-xylulose reductase.

Arabinose↗
PubMed1989

The effect of aldose reductase inhibition on erythrocyte polyols and galactitol accumulation in diabetic patients.

Erythrocyte sorbitol level has previously been used as a measure of the efficacy of aldose reductase inhibitors, but its value is limited by fluctuations related to variations in blood glucose concentration. The aim of the study was to compare sorbitol content with the ability to accumulate galactitol during ex vivo incubation with galactose, of erythrocytes taken from diabetic patients following administration of a single 600 mg dose of the aldose reductase inhibitor, ponalrestat. Twelve patients were studied in a placebo-controlled crossover trial. Blood glucose levels were not statistically different during the placebo and ponalrestat treatment periods except at 1 h after the dose was taken (10.6 +/- 6.7 vs 7.7 +/- 4.6 mmol l-1 (+/- SD), p less than 0.05). Ponalrestat reduced erythrocyte sorbitol concentrations compared with placebo at 3, 5 and 7 h (0.82 +/- 0.36, 0.69 +/- 0.23, and 0.83 +/- 0.35 mg l-1 vs 1.79 +/- 0.67, 1.68 +/- 0.65, and 1.57 +/- 0.59 mg l-1 respectively, p less than 0.005) and 24 h post-dose (1.57 + 0.45 vs 2.01 + 0.73 mg l-1, p less than 0.05). Ponalrestat also reduced erythrocyte galactitol accumulation at 3, 5 and 24 h post-dose from 5.53 +/- 2.41, 5.43 +/- 1.89, and 5.42 +/- 1.96 mg l-1 2-h-1 to 1.47 +/- 0.30, 1.76 +/- 0.41, and 4.12 +/- 0.72 mg l-1 2-h-1 respectively, p less than 0.01. Galactitol accumulation rate appeared to be a less variable parameter than erythrocyte sorbitol and was not influenced by fluctuations in blood glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehyde Reductase↗
PubMed1982

Xylitol-mediated transient inhibition of ribitol utilization by Lactobacillus casei.

The growth of Lactobacillus casei strain Cl-16 at the expense or ribitol was inhibited if the non-metabolizable substrate xylitol was included in the medium at concentrations of 6 mM or greater. At these concentrations, xylitol, did not competitively inhibit ribitol transport. The cessation of growth was caused by the intracellular accumulation of xylitol-5-phosphate, which occurred because growth on ribitol had gratuitously induced a functional xylitol-specific phosphotransferase system but not the enzymes necessary for the further metabolism of xylitol-5-phosphate. Eventually, the cells overcame the xylitol-mediated inhibition by repressing the synthesis of enzyme II of the xylitol phosphotransferase system so that xylitol-5-phosphate would no longer be accumulated within the cell.

Bacterial Proteins↗
PubMed1986

The polyol pathway in retinal microangiopathy.

Two structurally unrelated aldose reductase inhibitors (sorbinil and tolrestat) were used for assessing the possible role of aldose reductase in the thickening of retinal capillary basement membranes of rats. Rats were fed either a normal diet, a 50% galactose diet, or a 50% galactose diet with the addition of an aldose reductase inhibitor. Micrographs of capillaries in the outer plexiform layer of the retina were analysed. This showed that the basement membrane thickening and the ultrastructural changes in the retinal capillaries that were induced by the galactose diet were inhibited by the addition of an aldose reductase inhibitor. Thickening of the basement membrane may be related to other tissue lesions in diabetic retinopathy. Therefore, its prevention might have a favourable influence on other aspects of this retinopathy.

Aldehyde Reductase↗