Rapid and sensitive, colorimetric determination of the anomers of D-glucose with D-glucose oxidase, peroxidase, and mutarotase

Protective effect of cinnamon on diabetic cardiomyopathy in nicotinamide-streptozotocin induced diabetic rat model

There is an increase in the incidence and prevalence of type-2 diabetes and obesity which leads to the structural and functional changes in myocardium leading to a lethal complication called diabetic cardiomyopathy (DCM). In the present study, we investigated the preventive effect of cinnamon (3% of Cinnamomum zeylanicum bark powder in AIN-93 diet for 3 months) feeding on DCM and the concerned mechanisms in a rodent model. Experimental diabetes was induced by a single intraperitoneal injection of 40 mg/kg b.w streptozotocin (STZ), 15 min after the ip administration of 60 mg/kg b.w of nicotinamide (NA) in Wistar-NIN (WNIN) male rats. The oxidative stress parameters were investigated by assessing superoxide dismutase (SOD), glutathione-s-transferase (GST) enzyme activity, protein carbonyls and malondialdehyde (MDA) levels. The histopathology of myocardium was analyzed by H&E and Masson's trichrome staining, and scanning electron microscopy. The changes in diabetic rat heart involved the altered left ventricular parietal pericardium, structural changes in myocardial cells, enhanced oxidative stress. Masson's trichrome and H&E staining have shown increased fibrosis, and perinuclear vacuolization in NA-STZ induced diabetic rat myocardium. Cinnamon feeding prevented the oxidative stress and myocardial alterations in the heart of diabetic rats. Taken together, these results suggest that cinnamon can effectively prevent the metabolic and structural changes in NA-STZ induced diabetic cardiomyopathy.

Discovery and characterization of a sulfoquinovose mutarotase using kinetic analysis at equilibrium by exchange spectroscopy

Bacterial sulfoglycolytic pathways catabolize sulfoquinovose (SQ), or glycosides thereof, to generate a three-carbon metabolite for primary cellular metabolism and a three-carbon sulfonate that is expelled from the cell. Sulfoglycolytic operons encoding an Embden–Meyerhof–Parnas-like or Entner–Doudoroff (ED)-like pathway harbor an uncharacterized gene (yihR in Escherichia coli; PpSQ1_00415 in Pseudomonas putida) that is up-regulated in the presence of SQ, has been annotated as an aldose-1-epimerase and which may encode an SQ mutarotase. Our sequence analyses and structural modeling confirmed that these proteins possess mutarotase-like active sites with conserved catalytic residues. We overexpressed the homolog from the sulfo-ED operon of Herbaspirillum seropedicaea (HsSQM) and used it to demonstrate SQ mutarotase activity for the first time. This was accomplished using nuclear magnetic resonance exchange spectroscopy, a method that allows the chemical exchange of magnetization between the two SQ anomers at equilibrium. HsSQM also catalyzed the mutarotation of various aldohexoses with an equatorial 2-hydroxy group, including d-galactose, d-glucose, d-glucose-6-phosphate (Glc-6-P), and d-glucuronic acid, but not d-mannose. HsSQM displayed only 5-fold selectivity in terms of efficiency (k_cat/K_M) for SQ versus the glycolysis intermediate Glc-6-P; however, its proficiency [k_uncat/(k_cat/K_M)] for SQ was 17 000-fold better than for Glc-6-P, revealing that HsSQM preferentially stabilizes the SQ transition state.

The crystal structure of the core domain of a cellulose induced protein (Cip1) from Hypocrea jecorina, at 1.5 Å resolution

In an effort to characterise the whole transcriptome of the fungus Hypocrea jecorina, cDNA clones of this fungus were identified that encode for previously unknown proteins that are likely to function in biomass degradation. One of these newly identified proteins, found to be co-regulated with the major H. jecorina cellulases, is a protein that was denoted Cellulose induced protein 1 (Cip1). This protein consists of a glycoside hydrolase family 1 carbohydrate binding module connected via a linker region to a domain with yet unknown function. After cloning and expression of Cip1 in H. jecorina, the protein was purified and biochemically characterised with the aim of determining a potential enzymatic activity for the novel protein. No hydrolytic activity against any of the tested plant cell wall components was found. The proteolytic core domain of Cip1 was then crystallised, and the three-dimensional structure of this was determined to 1.5 Å resolution utilising sulphur single-wavelength anomalous dispersion phasing (sulphor-SAD). A calcium ion binding site was identified in a sequence conserved region of Cip1 and is also seen in other proteins with the same general fold as Cip1, such as many carbohydrate binding modules. The presence of this ion was found to have a structural role. The Cip1 structure was analysed and a structural homology search was performed to identify structurally related proteins. The two published structures with highest overall structural similarity to Cip1 found were two poly-lyases: CsGL, a glucuronan lyase from H. jecorina and vAL-1, an alginate lyase from the Chlorella virus. This indicates that Cip1 may be a lyase. However, initial trials did not detect significant lyase activity for Cip1. Cip1 is the first structure to be solved of the 23 currently known Cip1 sequential homologs (with a sequence identity cut-off of 25%), including both bacterial and fungal members.

Utilization of Shochu distillery wastewater for production of polyunsaturated fatty acids and xanthophylls using thraustochytrid

The industrial production of barley shochu, a distilled alcoholic beverage, results in distillery waste that is currently incinerated or disposed of in landfills, causing environmental pollution. The supernatant of distillery waste contains organic matter such as proteins ( approximately 2.5%) and amino acids ( approximately 0.2%). This study demonstrates that the utilization of distillery wastewater as a sole nitrogen source enables a marine thraustochytrid, Schizochytrium sp. strain KH105, to propagate and accumulate valuable lipids including docosahexaenoic acid (DHA) and astaxanthin. Under optimized culture conditions, the highest DHA and astaxanthin yields were obtained at 3.4 g/l and 7.7 mg/l, respectively, after 4 or 5 d of cultivation in a 3-l jar fermentor. The chemical oxygen demand of the wastewater was reduced by 35%. About 67% of crude protein content and 85% of total free amino acid content also decreased in the culture supernatant. The thraustochytrid therefore serves to upgrade the distillery by-product to one containing value-added lipids for functional foods as well as to regulate the environmental contamination.

Mechanism of action of theendo-(1 → 3)-α-glucanase MutAp from the mycoparasitic fungusTrichoderma harzianum

(1-->3)-alpha-glucanases catalyze the hydrolysis of fungal cell wall (1-->3)-alpha-glucan, and function during cell division of yeasts containing this cell wall component or act in mycoparasitic processes. Here, we characterize the mechanism of action of the (1-->3)-alpha-glucanase MutAp from the mycoparasitic fungus Trichoderma harzianum. We observed that MutAp releases predominantly beta-glucose upon hydrolysis of crystalline (1-->3)-alpha-glucan, indicating inversion of the anomeric configuration. After having identified (1-->3)-alpha-glucan tetrasaccharide as the minimal substrate for MutAp, we showed that reduced (1-->3)-alpha-glucan pentasaccharide is cleaved into a trisaccharide and a reduced disaccharide, demonstrating that MutAp displays endo-hydrolytic activity. We propose a model for the catalytic mechanism of MutAp, whereby the enzyme breaks an intrachain glycosidic linkage of (1-->3)-alpha-glucan, and then continues its hydrolysis towards the non-reducing end by releasing beta-glucose residues in a processive manner.

Role of altered renal lipid metabolism and the sterol regulatory element binding proteins in the pathogenesis of age-related renal disease

BACKGROUND

There are well-known changes in age-related renal function and structure, including glomerulosclerosis and decline in glomerular filtration rate (GFR). The purpose of this study was to identify a potential role for lipids in mediating age-related renal disease.

METHODS

Mice of five different age groups (3, 6, 12, 19, and 23 months old) were studied.

RESULTS

We have found that in C57BL/6 mice there was a progressive increase in age-related glomerulosclerosis [increase in periodic acid-Schiff (PAS) staining and accumulation of extracellular matrix proteins including type IV collagen and fibronectin], increased glomerular basement thickness and podocyte width and effacement, and increased proteinuria. These changes were associated with age-related increase in lipid accumulation as determined by increased Oil Red O staining in kidney sections. Biochemical analysis indicated that these lipid deposits corresponded to significant increases in renal triglyceride and cholesterol content. We have also found significant age-related increases in the nuclear transcription factors, sterol regulatory element-binding proteins (SREBP-1 and SREBP-2), protein abundance and increased expression or activity of their target enzymes that play an important role in lipid synthesis.

CONCLUSION

Our results indicated that there was an age-related increase in renal expression of SREBP-1 and SREBP-2 with resultant increases in lipid synthesis and triglyceride and cholesterol accumulation in the kidney. Because we have previously shown that increased expression of SREBPs in the kidney per se results in glomerulosclerosis and proteinuria, our data suggested that increased SREBPs' expression resulting in increased renal lipid accumulation may play an important role in age-related nephropathy.

Purification and characterization of an acid trehalase from Acidobacterium capsulatum

We purified an acid trehalase (EC 3.2.1.28, alpha,alpha'-trehalose glucohydrolase) from an acidophilic bacterium, Acidobacterium capsulatum. The enzyme was homogeneous based on polyacrylamide gel electrophoresis, and was composed of a single polypeptide chain with a molecular mass of 57 kDa. Maximum trehalase activity was observed at pH 2.5. The acid trehalase exhibited an apparent K(m) of 1.0 mM for trehalose at 30 degrees C and pH 3.0. The trehalase was located in the periplasmic space. The activity of the enzyme was activated by 1.0 mM MnCl2 or CoCl2, and inhibited by 1.0 mM PbCl2, HgCl2, NiCl2, p-chloromercuribenzoate, N-ethylmaleimide, monoiodoacetate, or EDTA. The enzyme showed high specificity for trehalose. It was found that an equimolar mixture of alpha-D-glucose and beta-D-glucose was formed on hydrolysis of trehalose by the trehalase.

Purification and characterization of an intracellular cycloalternan-degrading enzyme from Bacillus sp. NRRL B-21195

A novel intracellular cycloalternan-degrading enzyme (CADE) was purified to homogeneity from the cell pellet of Bacillus sp. NRRL B-21195. The enzyme has a molecular mass of 125 kDa on SDS-PAGE. The pH optimum was 7.0, and the enzyme was stable from pH 6.0 to 9.2. The temperature optimum was 35 degrees C and the enzyme exhibited stability up to 50 degrees C. The enzyme hydrolyzed cycloalternan [CA; cyclo(-->6)-alpha-d-Glcp-(1-->3)-alpha-d-Glcp-(1-->6)-alpha-d-Glcp-(-->3)-alpha-d-Glcp-(1-->)] as the best substrate, to produce only isomaltose via an intermediate, alpha-isomaltosyl-(1-->3)-isomaltose. This enzyme also hydrolyzed isomaltosyl substrates, such as panose, alpha-isomaltosyl-(1-->4)-maltooligosaccharides, alpha-isomaltosyl-(1-->3)-glucose, and alpha-isomaltosyl-(1-->3)-isomaltose to liberate isomaltose. Neither maltooligosaccharides nor isomaltooligosaccharides were hydrolyzed by the enzyme, indicating that CADE requires alpha-isomaltosyl residues connected with (1-->4)- or (1-->3)-linkages. The K(m) value of cycloalternan (1.68 mM) was 20% of that of panose (8.23 mM). The k(cat) value on panose (14.4s(-1)) was not significantly different from that of cycloalternan (10.8 s(-1)). Judging from its specificity, the systematic name of the enzyme should be cycloalternan isomaltosylhydrolase. This intracellular enzyme is apparently involved in the metabolism of starch via cycloalternan in Bacillus sp. NRRL B-21195, its role being to hydrolyze cycloalternan inside the cells.

A synergistic reaction mechanism of a cycloalternan-forming enzyme and a d-glucosyltransferase for the production of cycloalternan in Bacillus sp. NRRL B-21195

Cycloalternan-forming enzyme (CAFE) was first described as the enzyme that produced cycloalternan from alternan. In this study, we found that a partially purified preparation of CAFE containing two proteins catalyzed the synthesis of cycloalternan from maltooligosaccharides, whereas the purified CAFE alone was unable to do so. In addition to the 117 kDa CAFE itself, the mixture also contained a 140 kDa protein. The latter was found to be a disproportionating enzyme (DE) that catalyzes transfer of a D-glucopyranosyl residue from the non-reducing end of one maltooligosaccharide to the non-reducing end of another, forming an isomaltosyl residue at the non-reducing end. CAFE then transfers the isomaltosyl residue to the non-reducing end of another isomaltosyl maltooligosaccharide, to form an alpha-isomaltosyl-(1-->3)-alpha-isomaltosyl-(1-->4)-maltooligosaccharide, and subsequently catalyzes a cyclization to produce cycloalternan. Thus, DE and CAFE act synergistically to produce cycloalternan directly from maltodextrin or starch.

A new enzyme, maltobionate alpha-D-glucohydrolase, from alkalophilic Bacillus sp. N-1053

A new enzyme, maltobionate alpha-D-glucohydrolase, was purified to apparent homogeneity from a cell-free extract of alkalophilic Bacillus sp. N-1053 about 930-fold with a yield of 18% and some of its properties were investigated. The enzyme showed optimum activity at about pH 7.0, and was stable over the range of pH 6.0-9.5. The molecular weight was estimated to be 152,000 and 71,000 by HPLC gel filtration on TSKgel G3000SWXL and SDS-polyacrylamide gel electrophoresis, respectively. The enzyme hydrolyzed maltobionate more effectively than disaccharides such as maltose and maltitol or trisaccharides such as maltotrionate, maltotriose and maltotriitol, but showed no activity toward polysaccharides such as amylose, amylopectin and soluble starch. The reaction products from 1 mol of maltobionate were found to be 1 mol of beta-D-glucose and 1 mol of D-gluconate. The Km value for maltobionate was 1.63 mM and the Vmax/Km value for maltobionate was the largest among the substrates tested. The enzyme activity was almost completely inhibited by Hg2+, Ag+, iodine and N-bromosuccinimide, and also inhibited by p-nitrophenyl alpha-D-glucoside, maltose and maltitol.

Alpha- and beta-anomeric preference of glucose-induced insulin secretion at physiological and higher glucose concentrations, respectively

We determined the anomeric preference of glucose phosphorylation by islet glucokinase, glucose utilization by pancreatic islets, and insulin secretion induced by glucose over a wide range of glucose concentrations. alpha-D-Glucose was phosphorylated faster than beta-D-glucose by islet glucokinase at lower glucose concentrations (5 and 10 mM), whereas the opposite anomeric preference was observed at higher glucose concentrations (40 and 60 mM). At 20 mM, there was no significant difference in phosphorylation rate between the two anomers. Similar patterns of anomeric preference were observed both in islet glucose utilization and in glucose-induced insulin secretion. The present study affords strong evidence that glucokinase is responsible for the anomeric preference of glucose-stimulated insulin secretion through anomeric discrimination in islet glucose utilization.

Cloning and expression of the Acinetobacter calcoaceticus mutarotase gene in Escherichia coli

This article describes the cloning of the mutarotase gene from Acinetobacter calcoaceticus and its expression in Escherichia coli. Purification of mutarotase (EC 5.1.3.3) led to a single polypeptide of 40 kilodaltons. The sequences of 27 N-terminal and 76 C-terminal amino acids were determined. From six amino acids of the N-terminal and seven amino acids of the C-terminal portion of the protein, the sequences of two oligonucleotides were deduced. These were synthesized and used as gene probes. Completely restricted chromosomal DNA from A. calcoaceticus was size fractioned, and only fractions hybridizing with the gene probes were used to construct gene banks enriched for the mutarotase determinant. With the N-terminal gene probe, a bank of 6- to 7-kilobase-pair BclI fragments in pBR327 was obtained. A total of 1,200 candidates were screened by colony hybridization followed by dot-blot analysis of purified plasmids from positive candidates and subsequent Southern blot analysis of the respective restricted plasmids, and 500 base pairs (bp) from the 5' end of the mutarotase gene were isolated by this procedure. The 3' portion of the gene was isolated from a gene bank containing 1,500-bp-long HindIII fragments inserted in M13mp11. This bank was screened by dot-blot analysis of single-stranded phage DNA with the C-terminal gene probe. The isolated gene fragments were fused at a common restriction site in their overlapping region to yield the complete mutarotase gene. High-level expression of mutarotase in E. coli was achieved when the gene was placed under transcriptional control of the phage lambda promoter pL. More than 90% of mutarotase activity was found in the culture medium. The E. coli-derived mutarotase was purified and shown to be identical to the A. calcoaceticus-derived product with respect to the molecular weight and N-terminal amino acid sequence. The expression of mutarotase in E. coli was increased 200-fold in comparison to that the wild-type A. calcoaceticus.

Preventive effects of cyclosporin on diabetes in NOD mice

Non-obese diabetic mice aged 30 to 60 days were treated orally with Cyclosporin at doses of 25, 15 and 2.5 mg/kg every 2 days until 160 days of age. Diabetes developed in 12 out of 18 oil-treated mice (67%), with partial to complete Langerhans' islet destruction associated with lymphocytic infiltration. The non-obese diabetic mice showed a plasma glucose concentration of 6.62 +/- 0.92 mmol/l (mean +/- SD) at 50 days of age. The plasma glucose level of oil-treated non-obese diabetic mice gradually increased after 130 days of age and reached 14.0 to 19.0 mmol/l at 160 days of age, while Cyclosporin-treated non-obese diabetic mice showed neither clear increase of plasma glucose levels nor development of insulitis. The cumulative incidence of diabetes in Cyclosporin-treated mice was significantly lower than that in oil-treated mice (p less than 0.01). Subsequently, Cyclosporin treatment was started after development of glucose intolerance. Twenty-five mg/kg of Cyclosporin was administered every 2 days for 35 days. Cyclosporin appeared to have little therapeutic effect on diabetes in non-obese diabetic mice.

Anomeric compositions of D-glucose in tissues and blood of rat

The anomeric compositions of D-glucose in the liver, kidney, heart, blood and plasma of rat were determined by our methods for the assay of D-glucose anomers and the percentages of the beta-anomer were found to be 61.8, 61.0, 62.4, 62.7 and 62.9, respectively.