Functional significance of amylase polymorphism in Drosophila melanogaster. III. Ontogeny of amylase and some α-glucosidases

Changes in amylase (E.C. 3.2.1.1), maltase (E.C. 3.2.1.20), sucrase, and PNPGase activities in relation to changes in wet weight and protein content were studied during the development of larvae and adult flies from two strains of Drosophila melanogaster, homozygous for different amylase alleles. All -glucosidase activities increase exponentially during a large part of larval development, parallel to the increase in weight, and drop at the end of the third instar. Amylase activity of the Amy ¹ strain follows the same pattern. In contrast, amylase activity of the Amy ^4,6 strain continues its exponential increase longer. In the third larval instar amylase activity in the Amy ^4,6 strain becomes much higher than in the Amy ¹ strain. During the first hours of adult life amylase activity of the two strains does not differ. Then Amy ^4,6 activity starts to rise and becomes much higher (4–5 times) than Amy ¹ amylase activity, which remains approximately constant. All adult enzyme activities are much higher than in larvae. Comparison of enzyme activity of amylase and -glucosidases in larvae and adults confirms that differences in amylase activities can become important only when starch is a limiting factor in the food.The investigations were supported by the Foundation for Fundamental Biological Research (BION), which is subsidized by the Netherlands Organization for the Advancement of Pure Research (Z.W.O.).     

Glucose and glycerol repression of α-amylase in Streptomyces kanamyceticus and isolation of deregulated mutants

Summary Glucose and glycerol at concentrations of 2 % negatively affected amylase synthesis in plate and submerged Streptomyces kanamyceticus cultures. This microorganism was insensitive to growth inhibition by glucose analogs and deregulated mutants were identified by a clearing zone around colonies grown on starch and glycerol or glucose, and selected. Three kinds of mutants were obtained: one insensitive to glucose (Mutant 41), another insensitive to glycerol repression (Mutant E) and the last (Mutant 29) an amylase-hyperproducing mutant, albeit regulated by glucose or glycerol like the wild type. The levels of glucokinase, an enzyme involved in catabolite regulation of Enterobacteria, were determined and results showed no differences between the parental strain and the mutants.     

Purification and characterization of α-glucosidase in Apis cerana indica

Apis cerana indica foragers were used for the isolation of a full-length α- glucosidase cDNA, and for purification of the active nascent protein by low salt extraction of bee homogenates, ammonium sulphate precipitation and diethylaminoethyl-cellulose and Superdex 200 c hromatographies. The molecular mass of the purified protein was estimated by polyacrylamide gel electrophoresis resolution, and the pH, temperature, incubation, and substrate optima for enzymic activity were determined. Conformation of the purified enzyme as α-glucosidase was performed by BLAST software homology comparisons between matrix assisted laser desorption ionization time of flight mass spectroscopy analysed partial tryptic peptide digests of the purified protein with the predicted amino acid sequences deduced from the α-glucosidase cDNA sequence.     

Coexpression of α-l-arabinofuranosidase and β-glucosidase in Saccharomyces cerevisiae

Monoterpenes are important aroma compounds in grape varieties such as Muscat, Gewürztraminer and Riesling, and are present as either odourless, glycosidically bound complexes or free aromatic monoterpenes. Commercial enzymes can be used to release the monoterpenes, but they commonly consist of crude extracts that often have unwanted and unpredictable side-effects on wine aroma. This project aims to address these problems by the expression and secretion of the Aspergillus awamoriα-l-arabinofuranosidase in combination with either the β-glucosidases from Saccharomycopsis fibuligera or from Aspergillus kawachii in the industrial yeast Saccharomyces cerevisiae VIN13. The concentration of five monoterpenes was monitored throughout alcoholic fermentation of Gewürztraminer grapes. The recombinant yeast strains that caused an early boost in the geraniol concentration led to a reduction in the final geraniol levels due to the downregulation of the sterol biosynthetic pathway. Monoterpene concentrations were also analysed 9 and 38 days after racking and the performance of the VB2 and VAB2 recombinant strains was similar, and in many cases, better than that of a commercial enzyme used in the same experiment. The results were backed by sensorial analysis, with the panel preferring the aroma of the wines produced by the VAB2 strain.     

Thermostable extracellular α-amylase and α-glucosidase ofLipomyces starkeyi

Summary Thermostable, extracellular -amylase and -glucosidase were produced byLipomyces starkeyi CBS 1809 in a medium containing maize starch and soya bean meal. Contrary to published findings which suggested a single cell-bound amylolytic system for another strain ofL. starkeyi, this study revealed the presence of two enzymes — an -amylase and an -glucosidase inL. starkeyi CBS 1809. The enzymes were separated by solvent and salt precipitation and ion-exchange chromatography on DEAE-Biogel-A. The -amylase and -glucosidase had pH optima at 4.0 and 4.5 and temperature optima at 70°C and 60°C, respectively. While the low pH optima are not unique the enzymes are very distinctive in yeasts in having very high temperature optima. The -glucosidase had highest activities on maltose and isomaltose (100) with relative rates of activity on maltotriose, isomaltotriose and p-nitrophenyl--d-glucoside of 59, 48 and 22, respectively. It was inactive towards sucrose. Both the -amylase and -glucosidase ofL. starkeyi were located extracellularly and had molecular weights of 76,000 and 35,000, respectively.     

Comparison of α-glucosidase and α-mannosidase in bloodstream forms of Trypanosoma brucei brucei

• 1.1. The physicochemical and kinetic properties of the two major trypanosomal glycosidases, α-glucosidase (EC 3.2.1.20) and α-mannosidase (EC 3.2.1.24), were compared in bloodstream forms of Trypanosoma brucei brucei S42.
• 2.2. Both enzymes are membrane-bound and located intracellularly.
• 3.3. The results are discussed in relation to the possible role of α-glucosidase and α-mannosidase in the processing or catabolism of trypanosomal glycoproteins.

     

Benzimidazole derivatives as new α-glucosidase inhibitors and in silico studies

Newly synthesized benzimidazole hydrazone derivatives 1–26 were evaluated for their α-glucosidase inhibitory activity. Compounds 1–26 exhibited varying degrees of yeast α-glucosidase inhibitory activity with IC₅₀ values between 8.40 ± 0.76 and 179.71 ± 1.11 μM when compared with standard acarbose. In this assay, seven compounds that showed highest inhibitory effects than the rest of benzimidazole series were identified. All the synthesized compounds were characterized by different spectroscopic methods adequately. We further evaluated the interaction of the active compounds with enzyme with the help of docking studies.     

Expression of enzymatically active,recombinant barley α-glucosidase in yeast and immunological detection of α-glucosidase from seed tissue

An -glucosidase cDNA clone derived from barley aleurone tissue was expressed in Pichia pastoris and Escherichia coli. The gene was fused with the N-terminal region of the Saccharomyces cerevisiae -factor secretory peptide and placed under control of the Pichia AOX1 promoter in the vector pPIC9. Enzymatically active, recombinant -glucosidase was synthesized and secreted from the yeast upon induction with methanol. The enzyme hydrolyzed maltose > trehalose > nigerose > isomaltose. Maltase activity occurred over the pH range 3.5–6.3 with an optimum at pH 4.3, classifying the enzyme as an acid -glucosidase. The enzyme had a K_m of 1.88 mM and V_max of 0.054 µmol/min on maltose. The recombinant -glucosidase expressed in E. coli was used to generate polyclonal antibodies. The antibodies detected 101 and 95 kDa forms of barley -glucosidase early in seed germination. Their levels declined sharply later in germination, as an 81 kDa -glucosidase became prominent. Synthesis of these proteins also occurred in isolated aleurones after treatment with gibberellin, and this was accompanied by a 14-fold increase in -glucosidase enzyme activity.Abbreviations: AGL, barley seed -glucosidase; rAGL, recombinant barley seed -glucosidase; BMGY, buffered glycerol-complex medium; BMMY, buffered methanol-complex medium; GA, gibberellic acid; UTR, untranslated region.     

Multiple sugar binding sites in α-glucosidase

Twenty-five analogs of d-glucose were examined as reversible inhibitors of yeast α-glucosidase (EC 3.2.1.20). The K_i values range from 0.38 mM for 6-deoxy-d-glucose (quinovose) to 1.0 M for d-lyxose at pH=6.3 (0.1 M NaCl, 25°). All the monosaccharides and the three disaccharides (maltose, isomaltose and α,α-trehalose) were found to be linear competitive inhibitors with respect to α-p-nitrophenyl glucoside (pNPG) hydrolysis. Multiple inhibition analysis reveals that there are at least three monosaccharide binding sites on the enzyme. One of these can be occupied by glucose [K_i=1.8(±0.1) mM], one by d-galactose [K_i=164(±11) mM] and one by d-mannose [K_i=120(±9) mM]. The pH dependence for glucose binding closely follows that of V/K [pK_a1=5.55(±0.15), pK_a2=6.79(±0.15)], but the binding of mannose does not. Although the glucose subsite can be occupied simultaneously with the mannose or galactose subsites in the enzyme–product complex, no transglucosylation can be detected between pNPG and either mannose or galactose. This suggests that neither of these nonglucose subsites can be occupied in a productive manner in the covalent glucosyl-enzyme intermediate.     

Role of α-glucosidase in fetal lung maturation

The role of lysosomal enzyme acid α-glucosidase in fetal lung development was investigated with the aid of a specific inhibitor, the pseudosaccharide acarbose. The drug was added to a Waymouth culture medium of fetal rat lung expiants cultivated for 48 h from gestational stage 19.5 days, an in vitro system previously shown to allow morphological and biochemical maturation of alveolar epithelium. Glycogenolysis was reduced by 40% as compared with tissue cultivated on control medium, which means that α-glucosidase could account for as much as 40% of fetal lung glycogenolysis, the remaining 60% being presumably achieved by cytosolic phosphorylase and by a microsomal neutral α-glucosidase. By the same time, the increase of phospholipids of surfactant fraction extracted from cultivated expiants was partially inhibited: total and saturated phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylinositol were about 30–40% lower than in lungs cultivated on control medium. It should be emphasized that DNA concentration and increases in non-surfactant phospholipids were unchanged by the drug. α-Glucosidase activity was evidenced in the lysosomal fraction, in the microsomal fraction and, although in lower amounts, in the surfactant fraction extracted from term fetal lung. The results suggest that lysosomal α-glucosidase plays a major role in lung maturation and could facilitate glycogenolysis for the specific use of glycogen stores in providing substrates for surfactant phospholipid biosynthesis.     

Oxadiazoles and thiadiazoles: Novel α-glucosidase inhibitors

Oxadiazoles and thiadiazoles 1–37 were synthesized and evaluated for the first time for their α-glucosidase inhibitory activities. As a result, fifteen of them 1, 4, 5, 7, 8, 13, 17, 23, 25, 30, 32, 33, 35, 36 and 37 were identified as potent inhibitors of the enzyme. Kinetic studies of the most active compounds (oxadiazoles 1, 23 and 25, and thiadiazoles 35 and 37) were carried out to determine their mode of inhibition and dissociation constants K_i. The most potent compound of the oxadiazole series (compound 23) was found to be a non-competitive inhibitor (K_i = 4.36 ± 0.017 μM), while most potent thiadiazole 35 was identified as a competitive inhibitor (K_i = 6.0 ± 0.059 μM). The selectivity and toxicity of these compounds were also studied by evaluating their potential against other enzymes, such as carbonic anhydrase-II and phosphodiesterase-I. Cytotoxicity was evaluated against rat fibroblast 3T3 cell line. Interestingly, these compounds were found to be inactive against other enzymes, exhibiting their selectivity towards α-glucosidase. Inhibition of α-glucosidase is an effective strategy for controlling post-prandial hyperglycemia in diabetic patients. α-Glucosidase inhibitors can also be used as anti-obesity and anti-viral drugs. Our study identifies two novel series of potent α-glucosidase inhibitors for further investigation.     

Apyrase and α-glucosidase in the salivary glands of Aedes albopictus

An apyrase and an α-glucosidase were detected in the salivary glands extracts of adult Aedes albopictus. The apyrase is a 61,000 Da secreted protein that hydrolyses ATP and ADP. This protein is synthesized in adults and is preferentially accumulated in the distal lateral lobes of the female salivary glands. The α-glucosidase is a secreted 67,000 Da protein. This enzyme is synthesized during adult life and accumulated in the proximal-lateral lobes of both males and females. The results are discussed and compared with data previously obtained with Aedes aegypti salivary glands.     

Stablizing crude and ultrafiltrated α-amylase and α-glucosidase from Aspergillus oryzae by trehalose

Thermal resistance of freeze-dried -amylase and -glucosidase in trehalose matrices (1 to 20 % w/v) stored at 90 °C and relative humidities (RH) between 0 and 44 % was studied. At RH values up to 33 %, 10 % (w/v) trehalose was necessary to retain at least 50 % of -amylase activity. For -glucosidase, 10 % (w/v) trehalose was effective only at 0 % RH. Ultrafiltration of the crude enzymatic fermentation extracts enhanced enzyme stability per se. However, ultrafiltration in combination with 1 % (w/v) trehalose retained 74 % of -glucosidase and 95 % of -amylase activities. © Rapid Science Ltd. 1998     

The brown seaweed Sargassum hemiphyllum exhibits α-amylase and α-glucosidase inhibitory activity and enhances insulin release in vitro

Diabetes is one of the most prevalent chronic diseases globally. In this study, major polyphenols (17.35 ± 0.93–36.66 ± 2.01 mg/g) and minor fucoxanthin (non detected 15.12 ± 0.09 mg/g) were isolated from water, ethanol, and acetone extracts (WES, EES, and AES, respectively) of Sargassum hemiphyllum. Inhibition of α-amylase, α-glucosidase, sucrose, and maltase activities and stimulation of insulin secretion was greater with AES than with WES or EES and correlated with polyphenol and fucoxanthin concentrations in extracts. Moreover, 250 μg/ml EES and AES significantly increased insulin secretion in the presence of 25 mg/ml glibenclamide to higher levels than those obtained with 50 mg/ml glibenclamide. None of the extracts exhibited cytotoxicity, exacerbated the side effects of glibenclamide, or inhibited glibenclamide-induced insulin secretion. These results suggested that the S. hemiphyllum extracts WES, EES, and AES could be used as pharmaceuticals and functional foods to reduce dosages of synthetic diabetes drugs.     

Inhibitors of α-glucosidase, α-amylase and lipase from Chrysanthemum morifolium

A new endoperoxysesquiterpene lactone, 10α-hydroxy-1α,4α-endoperoxy-guaia-2-en-12,6α-olide (1), together with a flavanone, eriodictyol (2), and two flavone glycosides, acacetin-7-O-β-d-glucopyranoside (3) and acacetin-7-O-α-l-rhamopyranoside (4), were isolated from the methanol extract of Chrysanthemum morifolium flowers by a bioassay-guided fractionation. Compound 1 showed strong inhibitory effects against α-glucosidase and lipase activities, with IC₅₀ values of 229.3 and 161.0 μM, respectively. The flavone glycosides 3 and 4 inhibited both α-glucosidase and α-amylase, while flavanone 2 was only effective against α-amylase.     

Further purification and characterization of the acid α-glucosidase

1. Centrifugation of rat liver acid glucosidase, which had been purified by adsorption on dextran gel, on a density gradient of sucrose showed the enzyme to be impure. 2. Preliminary purification of the enzyme before the gel filtration improved the final degree of purity of this preparation. Disc gel electrophoresis of this preparation showed a single band of protein. 3. The sedimentation co-efficient and the molecular weight determined on a sucrose gradient were 4.9-5.1s and 76000-83000 respectively for the rat liver enzyme, and 5.6s and 97000 for the acid alpha-glucosidase purified by means of the same procedure from the human kidney. 4. The Michaelis constants of rat liver and human kidney enzyme were 4.7x10(-3)m and 13.6x10(-3)m respectively with maltose as substrate. 5. The enzyme from both tissues was inhibited by tris and by erythritol. The inhibition of the rat liver acid glucosidase by erythritol was competitive.     

Synthesis and activity of α-glucosidase produced byBifidobacterium pseudolongum

Bifidobacterium pseudolongum NCFB 2244 grew on starch as sole source of carbon and energy, but cell yields and specific growth rates were considerably lower than on glucose (=0.19±0.04 and 0.38±0.09 respectively). Amylase activity was not detected in cultures of this bacterium, but cell-associated -glucosidase was constitutively produced. Analysis of -glucosidase activity from cell extracts by preparative isoelectric focusing gave two peaks of activity with apparent isoelectric points of 3.9 (Enzyme I) and 4.2 (Enzyme II), corresponding to threefold and fourfold purification factors respectively. No -glucosidase activity was detected with Enzyme I after gel-filtration chromatography on Sephadex G150. However, activity was recovered in samples containing Enzyme II, indicating the protein had a molecular mass of approximately 126 kDa. This was subsequently confirmed by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). These results show that the restricted ability ofB. pseudolongum to utilize starch as a carbohydrate source is owing to synthesis of at least one, and possibly two, -glucosidase(s).     

The Genetics of Dopa Decarboxylase in DROSOPHILA MELANOGASTER . II. Isolation and Characterization of Dopa-Decarboxylase-Deficient Mutants and Their Relationship to the α-Methyl-Dopa-Hypersensitive Mutants

Of 84 lethals isolated over the dopa decarboxylase (DDC) deficiency Df(2L)50, 8 have been identified as DDC-deficient alleles on the basis of their effect on DDC activity when heterozygous over the CyO balancer chromosome with activities ranging from 28% to 53% of controls. Some of the Ddc-deficient alleles exhibit intracistronic complementation. Most of the complementing pairs of alleles are much reduced in viability, e.g. < 5% of expected, and express a common syndrome of mutant phenes which can reasonably be inferred to derive from inadequately sclerotinized cuticle. Individuals heterozygous for the noncomplementing allele, Ddcⁿ⁷, over the 12-band DDC deficiency, Df(2L)130, die at the end of embryogenesis as unhatched larvae with unpigmented mouth parts.

The Ddc alleles and the l(2)amd α-methyl dopa (αMD) hypersensitive alleles are both located within the 11 band region 37B10-C7. The l(2)amd locus is immediately to the right of hk(2–53.9).Ddc has been mapped within 0.004 Map Units to the right of l(2)amd with a maximum estimated recombination frequency of 0.01%. None of the Ddc/CyO strains are sensitive to the dietary administration of α-methyl dopa (αMD), and complementation occurs between the Ddc deficient alleles and the l(2)amd alleles both on the basis of viability and DDC activity. No effect on DDC by the amd alleles has been found to date. Even in the complementing heterozygote, amd^H1/amd ^H89, the level of activity, thermostability, and in vitro αMD inhibition of DDC remains unaffected. Although no biochemical phene has yet been established for the αMD hypersensitive amd alleles, it seems likely that the two groups of mutants are functionally related.