Cyanide Toxicity of Freshly Prepared Smoothies and Juices Frequently Consumed

AIMS

This study was conducted to detect the presence of cyanide in popular fruit and vegetable smoothies and juices marketed as raw and natural.

STUDY DESIGN

Eleven (11) popular varieties of drinks were analyzed for total cyanide (TCN). Drinks contained raw vegetables and fruits, flax seeds, whole apples with seeds, raw almond milk, and pasteurized almond milk as ingredients.

PLACE AND STUDY DURATION

Samples were collected from health food eateries located within Las Vegas, Nevada (USA) during the summer of 2017.

METHODOLOGY

Fifty milliliters (mL) of a homogenized smoothie and juice drink and 1 gram of flax seeds were subjected to the above-referenced methods for sample preparation per USEPA Methods 9012B (digestion) followed by USEPA method 9014 (colorimetry).

RESULTS

The highest TCN was detected in drinks containing raw flax seed followed by unpasteurized raw almond milk, then fresh whole apple juice. No TCN was observed in drinks that contained none of the above mentioned items (e.g. flax seed, raw almond milk) or those utilizing pasteurized ingredients.

CONCLUSION

This study observed that TCN is present in smoothies and juices containing raw flax seeds, fresh whole apples, and/or unpasteurized almond milk. Concentrations were detected as high as 341 μg L-1 in commercially available smoothies containing vegetables, raw flax seeds, almond milk and fruits. Smoothies with vegetables, fruits, unpasteurized almond milk, and no flax seeds contained 41 ug L-1 TCN, while similar smoothies with pasteurized almond milk contained negligible to 9.6 ug L-1 CN-. Unpasteurized almond milk and raw flax seeds were the major sources of TCN in drinks. With the increased demand for raw and natural foods, there is a potential sublethal exposure of TCN by consumers.

Galaxy evolution. Black hole feedback in the luminous quasar PDS 456

The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10(46) ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution.

Active galaxies. A fast and long-lived outflow from the supermassive black hole in NGC 5548

Supermassive black holes in the nuclei of active galaxies expel large amounts of matter through powerful winds of ionized gas. The archetypal active galaxy NGC 5548 has been studied for decades, and high-resolution x-ray and ultraviolet (UV) observations have previously shown a persistent ionized outflow. An observing campaign in 2013 with six space observatories shows the nucleus to be obscured by a long-lasting, clumpy stream of ionized gas not seen before. It blocks 90% of the soft x-ray emission and causes simultaneous deep, broad UV absorption troughs. The outflow velocities of this gas are up to five times faster than those in the persistent outflow, and, at a distance of only a few light days from the nucleus, it may likely originate from the accretion disk.

Reflection from the strong gravity regime in a lensed quasar at redshift z = 0.658

The co-evolution of a supermassive black hole with its host galaxy through cosmic time is encoded in its spin. At z > 2, supermassive black holes are thought to grow mostly by merger-driven accretion leading to high spin. It is not known, however, whether below z ≈ 1 these black holes continue to grow by coherent accretion or in a chaotic manner, though clear differences are predicted in their spin evolution. An established method of measuring the spin of black holes is through the study of relativistic reflection features from the inner accretion disk. Owing to their greater distances from Earth, there has hitherto been no significant detection of relativistic reflection features in a moderate-redshift quasar. Here we report an analysis of archival X-ray data together with a deep observation of a gravitationally lensed quasar at z = 0.658. The emission originates within three or fewer gravitational radii from the black hole, implying a spin parameter (a measure of how fast the black hole is rotating) of a = 0.87(+0.08)(-0.15) at the 3σ confidence level and a > 0.66 at the 5σ level. The high spin found here is indicative of growth by coherent accretion for this black hole, and suggests that black-hole growth at 0.5 ≤ z ≤ 1 occurs principally by coherent rather than chaotic accretion episodes.

A rapidly spinning supermassive black hole at the centre of NGC 1365

Broad X-ray emission lines from neutral and partially ionized iron observed in active galaxies have been interpreted as fluorescence produced by the reflection of hard X-rays off the inner edge of an accretion disk. In this model, line broadening and distortion result from rapid rotation and relativistic effects near the black hole, the line shape being sensitive to its spin. Alternative models in which the distortions result from absorption by intervening structures provide an equally good description of the data, and there has been no general agreement on which is correct. Recent claims that the black hole (2 × 10(6) solar masses) at the centre of the galaxy NGC 1365 is rotating at close to its maximum possible speed rest on the assumption of relativistic reflection. Here we report X-ray observations of NGC 1365 that reveal the relativistic disk features through broadened Fe-line emission and an associated Compton scattering excess of 10-30 kiloelectronvolts. Using temporal and spectral analyses, we disentangle continuum changes due to time-variable absorption from reflection, which we find arises from a region within 2.5 gravitational radii of the rapidly spinning black hole. Absorption-dominated models that do not include relativistic disk reflection can be ruled out both statistically and on physical grounds.

Sonochemical degradation of perchloroethylene: the influence of ultrasonic variables, and the identification of products

Sonochemistry is a technique that offers promise for pollutant degradation, but earlier studies on various chlorinated substrates do not give a definitive view of the effectiveness of this methodology. We now report a thorough study of ultrasonic operational variables upon perchloroethylene (PCE) degradation in water (variables include ultrasonic frequency, power and system geometry as well as substrate concentration) and we attempt to close the mass balance where feasible. We obtained fractional conversions of >97% showing very effective loss of pollutant starting material, and give mechanistic proposals for the reaction pathway based on cavitational phenomena inducing pyrolytic and free radical processes. We note major products of Cl(-) and CO(2)/CO, and also trichloroethylene (TCE) and dichloroethylene (DCE) at ppm concentrations as reported earlier. The formation at very low (ppb) concentration of small halocompounds (CHCl(3), CCl(4)) and also of higher-mass species, such as pentachloropropene, hexachloroethane, is noteworthy. But of particular importance in our work is the discovery of significant quantities of chloroacetate derivatives at ppm concentrations. Although these compounds have been described as by-products with other techniques such as radiolysis or photochemistry, this is the first time that these products have been identified in the sonochemical treatment of PCE; this allows a much more effective account of the mass balance and may explain earlier inconsistencies. This reaction system is now better identified, but a corollary is that, because these haloacetates are themselves species of some toxicity, the use of ultrasound here may not sufficiently diminish wastewater toxicity.

Electrochemical study of silver thiosulphate reduction in the absence and presence of ultrasound

The electrochemical reduction of silver thiosulphate was studied potentiostatically on platinum electrodes in the absence and presence of ultrasound (20 kHz). This system is irreversible and the reaction is both diffusion and kinetically controlled. The slowest step is the kinetic reaction especially the chemisorption of ions at the electrode surface. Ultrasound greatly improves the mass transport, which can be explained by changing from diffusion to mainly convection. This paper reports the effect of ultrasound upon electrode kinetic and mass-transport parameters at various RDE rotation speeds and ultrasonic intensities. It was found that the heterogeneous rate constant (kf) is improved in the presence of ultrasound due to the increase in the formal or standard heterogeneous rate constant (k0) (approximately by 10-fold under sonication).

Sonovoltammetric studies on copper in buffered alkaline solution

The effect of ultrasound on the voltammetry of copper in alkaline solution is reported. At pH 7 the electrode surface remains active after scanning to ca. +1.0 V (vs. SCE) and the effects of ultrasound show the expected substantial enhancement in limiting current due to improved mass transport under ultrasound. However at pH 9, whereas the silent scan is only slightly altered in gross detail from that obtained at pH 7, the sonicated scan is significantly different. This shows the expected current increase only up until ca. +0.6 V (vs. SCE), where there is a substantial loss of current showing a passivation phenomenon that is enhanced by ultrasound. In addition, during the reverse (reduction) scan under ultrasound an anodic peak appears. This suggests reactivation of the electrode during the cathodic sweep, possibly by reductive removal of a transient species from the electrode/(hydr)oxide interface at a potential where oxidation still occurs. Increasing the pH to 11 further shifts the cathodic peaks in the silent voltammogram.

Reconstitution of Nicotinic Acetylcholine Receptors into Gel-Protected Lipid Membranes

We report the functional reconstitution of nicotinic acetylcholine receptors into gel-protected bilayer lipid membranes using two different methods. In the first case, reconstitution was achieved by direct membrane formation from an emulsion of glycerol monooleate, hexane, and a membrane receptor extract. In the second case, incorporation was achieved via the fusion of vesicles from a preparation of membrane-bound receptors into preformed membranes after diffusion through the protective front gel layer. Measurement of the dc conductivity of the membranes in the presence of either acetylcholine or alpha-bungarotoxin was used to test for the functional activity of incorporated receptors.

The effect of ultrasound upon the oxidation of thiosulphate on stainless steel and platinum electrodes

Ultrasound was found to increase the oxidation peak current and hence the decomposition rate of thiosulphate 50-fold compared to silent conditions. The effects of the ultrasonic frequency (20 and 38 kHz) and power upon the electrochemical oxidation of thiosulphate in aqueous KCl (1 mol dm-3) at stationary stainless steel and platinum electrodes were studied chronoamperometrically and potentiostatically (at various scan rates). No sigmoidal-shaped voltammograms were observed for the redox couple S4O6(2-)/S2O3(2-) in the presence of ultrasound. However, application of ultrasound to this redox couple provided an increase in the oxidation peak current at the frequencies employed, the magnitude of which varied with concentration, scan rate and ultrasonic power. Under sonication at 20 and 38 kHz, the oxidation peak potential shifted anodically with increasing ultrasonic power. This anodic shift in potential may be due to the formation of hydroxyl radicals, changes in electrode surface composition and complex adsorption phenomena. The large increase in oxidation peak currents and the rates of decomposition of thiosulphate, in the presence of ultrasound, are explained in terms of enhanced mass transfer at the electrode due to cavitation and acoustic streaming together with microstreaming coupled with adsorption phenomena. It is also shown that changes in macroscopic temperature throughout the experiment are insufficient to cause the observed enhanced diffusion.

Specific electrochemical nitration of horse heart myoglobin

Earlier findings on electronitration of hen egg-white lysozyme demonstrated a product which was mononitrated at Tyr23, by ion-exchange chromatography, absorbance at 430 nm, dithionite reduction, and Edman sequencing of a nitrated proteolytic peptide. However, the whole protein was not sequenced; therefore, although the enzyme remained active upon nitration, reaction at other residues could not be completely eliminated. This study has now been extended to the redox protein myoglobin. We demonstrate the novel electronitration (electrooxidation in the presence of nitrite) of a specific tyrosine residue in horse heart myoglobin and also in apomyoglobin. Production of the yellow chromophore, 3-nitrotyrosine (3-NT), was apparent in apomyoglobin from A430 but was masked in holomyoglobin by the Soret band. In both cases, the presence of 3-NT in the electronitrated samples was further indicated by the binding of antibody to 3-NT in Western blots. High-resolution electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) mass spectrometry revealed a reaction product at [M + 45] (consistent with substitution of NO2 for H), indicating that the nitration reaction is the only reaction occurring which gives rise to a change in mass in the electrooxidation. Fragmentation mass spectrometry identified the nitration site as Tyr103, with no nitration at Tyr146. The procedure may be useful in preparing model nitrated proteins for the study of disease mechanisms.

The effects of tyrosine nitration on the structure and function of hen egg-white lysozyme

We have investigated the effects of tyrosine nitration (to form the weak acid, 3-nitrotyrosine) at positions 23 or 20 plus 23, on the structure and function of hen egg-white lysozyme. Enzyme activity against Micrococcus luteus cell-wall fragments or soluble substrates exhibits two phenomena. (a) A decrease in Km and kcat for the hydrolysis of soluble oligo- and poly-saccharides, resulting in only minor changes in the catalytic efficiency (kcat/Km) upon nitration. (b) The hydrolysis of M. luteus cell-wall fragments appeared to be dominated by electrostatic interactions with the protein, giving a decrease in enzyme activity as the 3-nitrotyrosyl group became ionized. Removal of the cell-wall anionic polymer, teichuronic acid, from M. luteus abolished this effect. The 3-nitrotyrosine group was also found to act as a fluorescence quencher of exposed tryptophan residues in lysozyme.

Catalysis of reduction of carbohydrate 2-oxoaldehydes (osones) by mammalian aldose reductase and aldehyde reductase

In mammalian tissues, carbohydrate 2-oxoaldehydes, or 'osones', formed by cleavage of carbohydrate residues from glycated proteins, cause damage to cells and tissues by cross-linking of proteins. In the substrate specificity study reported here, we show that several osones are relatively good substrates for the reduced, unactivated form of aldose reductase (EC 1.1.1.21) from human and pig muscle, and aldehyde reductase (EC 1.1.1.2) from pig kidney, enzymes that have been well characterised both structurally and mechanistically. Since these enzymes are relatively ubiquitous, they may serve to protect a large number of tissues from damage, by catalysing the reduction of locally-produced osones. Reduction of all substrates by aldehyde reductase obeyed Michaelis-Menten kinetics. In contrast, a Hill constant of about 0.5 was obtained for aldose reductase-catalysed reduction of each of the carbohydrate 2-oxoaldehydes, and for several other substrates that were examined. Although this deviation from Michaelis-Menten kinetics has been ascribed to the presence of two forms of the enzyme, activated and unactivated, our results suggest that it is a characteristic of the unactivated form.

Electrochemical modification of lysozyme: anodic reaction of tyrosine residues

Preparative electrooxidation of lysozyme at copper electrodes held at potentials around 1.2 V vs. a saturated calomel reference electrode induces the formation of a yellow chromophore with a concomitant decrease in the pI of the protein. Ion-exchange high-performance liquid chromatography revealed two new lysozyme species with pI values of 10.8 and 10.7 (lysozyme-11.0) which bear the chromophore. Sequence analysis of these two species showed that protein with lower pI was modified at both Tyr 23 and Tyr 20 and the other exclusively at Tyr 23. ribonuclease A, subtilisin BPN', and BSA were also found to produce the same chromophore using similar electrochemical reaction schemes. Characterization of the chromophore by a variety of techniques revealed that it is apparently 3-nitrotyrosine.

Site specificity of glycation of horse liver alcohol dehydrogenase in vitro

The site specificity of in vitro glycation of horse liver alcohol dehydrogenase (ADH) was examined and the results interpreted in terms of structural features of the enzyme molecule. In a phosphate buffer solution, glycation occurred at Lys231 (the main site of glycation in vivo), at Lys228 (which is not glycated in vivo), and at several unidentified positions. Buffer anions or NAD+ did not affect glycation of Lys231; this supported our hypothesis that the base catalyst which removes a proton from carbon 2 of a Lys231-attached aldimine is part of the ADH molecule [Shilton, B.H. & Walton, D.J. (1991) J. Biol. Chem. 266, 5587-5592]. Use of a molecular modelling programme indicated that this catalyst was likely to be the imidazole group of His348, exerting its effect through the hydroxyl of Thr347. Glycation of Lys228 occurred only in the presence of phosphate; in this case molecular modelling showed that the base catalyst could be a phosphate ion, bound to ADH at a positive region of the coenzyme binding site. NAD+ inhibited glycation of Lys228 by binding to the enzyme and restricting access to glucose.

Sites of glycation of human and horse liver alcohol dehydrogenase in vivo

Sites of in vivo glycation of human and horse liver alcohol dehydrogenase were identified by cleavage of the borotritide-treated enzyme with trypsin, followed by gas-phase sequencing of the resulting tritium-labeled glycated peptides. A blank sequencing result, i.e. failure to detect an amino acid phenylthiohydantoin after completion of an Edman degradation cycle, was ascribed to an N-(1-deoxyhexitolyl)lysyl residue, which represented a glycation site on the original enzyme subunit. In human liver alcohol dehydrogenase the sites affected were the epsilon-amino groups of lysines 10, 39, 231, 248, and 325, which were glycated to the relative extents of 10, 5, 75, 5, and 5%, respectively. The site specificity of in vivo glycation of the horse enzyme is similar; 70-75% of it had occurred at lysine 231. A computer image of the crystal structure of horse liver alcohol dehydrogenase was examined. As a result, it was proposed that the high rate of glycation at lysine 231 is due to acid-base catalysis of the Amadori rearrangement by the imidazole group of histidine 348. This hypothesis was supported by showing that imidazole groups were close to sites of glycation in several other proteins.

Evidence for glycation of horse liver alcohol dehydrogenase in vivo

A procedure involving HPLC of N-phenylthiocarbamyl derivatives of N-(1-deoxyhexitolyl) amino acids was used to show that borohydride-treated alcohol dehydrogenase, from horse liver, contained 0.16 mol of N epsilon-(1-deoxyhexitolyl) lysine per mol of enzyme. The identity of this compound was confirmed by mass spectrometry. It was concluded that glycation of alcohol dehydrogenase had occurred in vivo, resulting in the formation of N epsilon-(1-deoxyfructosyl) lysyl residues. The presence of the latter accounted for the retention of 14% of the enzyme by an agaroseboronate gel. These findings are interesting in view of the observation [Tsai, C. S., and White, J. H. (1983) Biochem. J. 209, 309-314] that the enzyme was activated when it was glycated in vitro.

Role of fructose in glycation and cross-linking of proteins

Incubation of carbohydrate-free human serum albumin (HSA) with fructose in an aqueous buffer at pH 7.4 resulted in glycation of epsilon-amino groups of lysyl residues. A recently developed procedure, involving analysis of hexitol amino acids by high-performance liquid chromatography of phenylthiocarbamyl derivatives, was used to show that 85% of the bound hexose was attached to protein via carbon 2 (C-2). The remainder was attached to protein via carbon 1 (C-1). When incubations were conducted with glucose under identical conditions, all the hexose was attached via C-1. Examination of human ocular lens proteins showed that the majority of the covalently bound hexose was connected to epsilon-amino groups of lysyl residues via C-1; this was attributed mainly to nonenzymatic glucosylation in vivo, which has already been documented. A significant proportion (10-20%) of the bound hexose was connected via C-2. In view of the HSA-hexose incubation results (above), this indicated that the lens proteins had reacted with endogenous fructose; i.e., they had undergone nonenzymatic fructosylation in vivo. The model protein bovine pancreatic ribonuclease A reacted with fructose and glucose at similar rates under physiological conditions. However, covalent, non-disulfide cross-linking, which could be inhibited by D-penicillamine, was induced 10 times more rapidly by fructose than by glucose. It is postulated that some of the protein cross-linking that occurs in vivo is fructose-induced. The possible significance of these processes in diabetic subjects is discussed.

Order of enzymic incorporation of O-methyl groups into the O-methyl-D-glucose-containing polysaccharide of Mycobacterium smegmatis. A tritium-labelling study

The order of enzymic incorporation of O-methyl groups into the O-methyl-D-glucose-containing polysaccharide (MGP) of Mycobacterium smegmatis, 3MG(J)----G(I)----G(H) ----G(G)----6MG(F)----(GMG)9(E)----[G(L)----G(D)]----G(C) ----[G(K)----G(B)]----G(A)----Ga, where G is D-glucose, 3MG is 3-O-methyl-D-glucose, 6MG is 6-O-methyl-D-glucose, and Ga is D-glyceric acid, was studied by incubating cultures of M. smegmatis with L-[3H-Me]methionine for various times. MGP was then extracted from the cells, and relative radioactivities of residues D, (E + F)average and J, or of D, E average, F, and J, were determined. Tritium-labelling of these residues increased in the reducing-to-nonreducing residue direction, the steepness of the gradient becoming more shallow with increasing incubation time. The results are consistent with a biosynthetic mechanism that involves sequential addition of O-methyl groups to residues of the pre-formed D-glucan, in the reducing-to-nonreducing residue direction.

Analysis of glycated amino acids by high-performance liquid chromatography of phenylthiocarbamyl derivatives

A method has been developed for the analysis of hexitolamino acids formed by acid-catalyzed hydrolysis of nonenzymatically glycated proteins that have been treated with sodium borohydride. The hexitolamino acids are converted into phenylthiocarbamyl (PTC) derivatives which are analyzed by reverse-phase HPLC. The PTC derivatives of N alpha-hexitolamino acids behave like lactones, migrating on the column more slowly than the corresponding PTC-amino acids. The PTC derivatives of N epsilon-glucitol- and N epsilon-mannitol-lysine are probably free acids, since they migrate faster than PTC-lysine. The method, which can be used to determine the degree of glycation of N-terminal and lysyl residues, has been applied successfully to human hemoglobin, serum albumin, and ocular lens proteins.

Non-enzymic glycation of proteins: analysis of N-(1-deoxyhexitol-1-yl)amino acids by high-performance liquid chromatography

A method for determining the extent of non-enzymic glycation (originally called "glycosylation") of both lysyl and N-terminal residues of a protein is described. The glycated protein is treated with sodium borohydride, and is then subjected to acid-catalysed hydrolysis. The resulting N-(1-deoxy-D-hexitol-1-yl)amino acids are separated by cation-exchange high-performance liquid chromatography (l.c.), and detected by a post-column reaction with periodate. The method has been applied successfully to samples of human hemoglobin and human serum albumin, for measurement of numbers of valine-attached and of lysine-attached N-(1-deoxy-D-fructos-1-yl) groups per protein molecule.

Analysis of bound carbohydrates of human lens fractions by gas-liquid chromatography

The bound carbohydrates of noncataractous , decapsulated, human lenses have been examined. The hexoses and hexosamines of the water-soluble, water-insoluble nonmembrane, and membrane fractions of lenses from six age groups were determined by gas-liquid chromatography. The plasma membrane contains 60-70% of all bound carbohydrates, including glucose, galactose, mannose, fucose, glucosamine, and galactosamine. These also occur in the water-insoluble nonmembrane fraction, suggesting that the latter contains glycoproteins. The water-soluble fraction contains glucose, galactose, and mannose.

Synthesis of N-(1-deoxyhexitol-1-yl)amino acids, reference compounds for the nonenzymic glycosylation of proteins

The N-(1-deoxy-D-mannitol-1-yl) and N-(1-deoxy-D-glucitol-1-yl) derivatives of L-valine, L-alanine, L-threonine, and L-leucine were prepared by reductive amination of D-mannose and D-glucose with the appropriate amino acids, in the presence of sodium cyanoborohydride. N epsilon-(1-Deoxy-D-mannitol-1-yl)- and N epsilon-(1-deoxy-D-glucitol-1-yl)-L-lysine were prepared by similar reactions of hexoses with N alpha-tert-butoxycarbonyl and N alpha-benzyloxycarbonyl-L-lysine, followed by removal of the protecting groups. The structures were confirmed by 1H-n.m.r. spectroscopy, which showed that each compound was completely free of its C-2 epimer. The synthetic compounds may be used as reference compounds for the identification of N-(1-deoxyhexitol-1-yl)amino acids formed when N-(1-deoxy-D-fructose-1-yl) groups of nonenzymically glycosylated proteins, of the hemoglobin A1c type, are reduced with sodium borohydride, and the protein is subjected to acid-catalyzed hydrolysis.

A compound representing the D-glycerate terminus of the methylglucose-containing polysaccharide of Mycobacterium smegmatis

In order to study the structure of the methylglucose-containing polysaccharide (MGP) of Mycobacterium smegmatis by NMR spectroscopy, we have prepared the model compound O-alpha-D-glucopyranosyl-(1 leads to 2)-D-glyceric acid. This compound, which represents the aglycon-containing terminus of MGP, was made from leucorse [O-alpha-D-glucopyranosyl-(1 leads to 5)-D-fructopyranose] by successive treatment with sodium borohydride, lead tetraacetate, and hypobromite. The structure of O-alpha-D-glucopyranosy.-(1 leads to 2)-D-glyceric acid was confirmed by chemical and enzymic methods. 13C and 1H NMR spectra of this compound, together with spectra of several disaccharides, were obtained for future reference in the polysaccharide study. The nine resonances in the 13C spectrum were assigned by comparison with the spectrum of methyl alpha-D-glucopyranoside. Analysis of the 1H NMR spectrum showed that the two methylene protons on C-3 of the glycerate moiety were less equivalent in the sodium salt than in the acid. This may be attributable to hydrogen bonding between the carboxylate and the hydrogen atom of the glycerate 3-hydroxyl group.

A comparative study of the tissue and species distribution of NADPH-dependent aldehyde reductase

1. NADPH-dependent aldehyde reductase (AR) is widely distributed among animal species. It also occurs in flowering plants and fungi (yeast). 2. AR is located mainly in the kidney or renal tissue of all species examined, with the exception of fish where it occurs mainly in the liver. 3. The enzyme from each species is monomeric and has a molecular weight between 30,000 and 40,000 daltons. 4. The enzymes exhibit similar substrate specificities and pH profiles and are inhibited by barbiturates. 5. In the reduction of D-glyceraldehyde the monomeric AR of each species catalyzes the stereospecific transfer of the A hydrogen from NADPH.

Properties of the nicotinamide adenine dinucleotide phosphate-dependent aldehyde reductase from pig kidney. Amino acid composition, reactivity of cysteinyl residues, and stereochemistry of D-glyceraldehyde reduction

Some physical and chemical properties of the monomeric NADP+-dependent aldehyde reductase (previously called TPN-L-hexonate dehydrogenase or D-glucuronate reductase) from pig kidney have been examined. The amino acid composition has been determined. Four of the five thiol groups react with p-mercuribenzoate at pH 7, with no resulting loss of catalytic activity. High concentrations of p-mercuribenzoate cause complete enzyme inhibition, which can be partly reversed by addition of aldehyde reductase is low (9%, estimated from the ellipticity at 208 nm), and 70 to 80% of the tyrosine and tryptophan residues aare buried within the molecule. One molecule of NADPH binds to the enzyme (Kp equal 25 muM), causing a blue shift and enhancement of the coenzyme fluorescence, and suggesting that the environment of the active site is hydrophobic. In the reduction of D-glyceraldehyde, catalyzed by aldehyde reductase, the pro-4R "A" hydrogen of NADPH attacks the re face of the carbonyl group. This stereospecificity is the same as in the reductions of D-glyceraldehyde and acetaldehyde effected by rabbit muscle dehydrogenase and liver alcohol dehydrogenase, respectively.

A new method of synthesis of aldosuloses

As a new approach to the synthesis of aldosuloses (osones), epimeric pairs of the allylic alcohols, 1 and 2, and 4 and 5, were oxidized to the corresponding vinyl ketones, 3 and 6, respectively. Degradation of the latter by reductive ozonolysis and hydrolysis gave D-glycero-tetrosulose and D-arabino-hexosulose (D-glucosone), respectively.