Journal of Microbiology

Journal Articles

The role of Jacalin-related lectin gene AOL_s00083g511 in the development and pathogenicity of the nematophagous fungus Arthrobotrys oligospora: Xinyuan Dong , Jiali Si , Guanghui Zhang , Zhen Shen , Li Zhang , Kangliang Sheng , Jingmin Wang , Xiaowei Kong , Xiangdong Zha , Yongzhong Wang; J. Microbiol. 2021;59(8):736-745. Published online July 5, 2021; DOI: https://doi.org/10.1007/s12275-021-1029-4

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Abstract: Arthrobotrys oligospora is a model species of nematophagous fungi and has great potential for the biological control of nematode diseases. Lectin is a protein that binds to carbohydrates and their complexes with high specificity, which mediates recognition events in various physiological and pathological processes. This study aimed to investigate the role of the Jacalin-related lectin (JRL) gene, AOL_s00083g511, in A. oligospora development. Through a homology recombination approach, we obtained the AOL_s00083g511 knockout mutant strain (Δg511). Next, the biological characteristics of the Δg511 mutant strain, including growth rate, conidia germination rate, adaptation to environmental stresses, and nematocidal activity, were compared with those of the wild-type (WT) strain. The results showed that the JRL gene AOL_ s00083g511 did not affect fungal growth, conidia germination, 3D-trap formation, and the ability of A. oligospora to prey on nematodes significantly. We speculate that this phenomenon may be caused by a loss of the key β1–β2 loops in the AOL_ s00083g511-encoded JRL domain and an intrinsic genetic compensation of AOL_s00083g511 in this fungus. The growth rates of both strains on high salt or surfactant media were similar; however, in the strong oxidation medium, the growth rate of the Δg511 mutant was significantly lower than that of the WT strain, indicating that AOL_s00083g511 might play a role in oxidative stress resistance. These findings provide a basis for further analysis of the related functions of the JRL gene in A. oligospora and their potential roles in the biological control of nematodes in the future.

Molecular characterization of Hsf1 as a master regulator of heat shock response in the thermotolerant methylotrophic yeast Ogataea parapolymorpha: Jin Ho Choo , Su-Bin Lee , Hye Yun Moon , Kun Hwa Lee , Su Jin Yoo , Keun Pil Kim , Hyun Ah Kang; J. Microbiol. 2021;59(2):151-163. Published online February 1, 2021; DOI: https://doi.org/10.1007/s12275-021-0646-2

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Abstract: Ogataea parapolymorpha (Hansenula polymorpha DL-1) is a thermotolerant methylotrophic yeast with biotechnological applications. Here, O. parapolymorpha genes whose expression is induced in response to heat shock were identified by transcriptome analysis and shown to possess heat shock elements (HSEs) in their promoters. The function of O. parapolymorpha HSF1 encoding a putative heat shock transcription factor 1 (OpHsf1) was characterized in the context of heat stress response. Despite exhibiting low sequence identity (26%) to its Saccharomyces cerevisiae homolog, OpHsf1 harbors conserved domains including a DNA binding domain (DBD), domains involved in trimerization (TRI), transcriptional activation (AR1, AR2), transcriptional repression (CE2), and a C-terminal modulator (CTM) domain. OpHSF1 could complement the temperature sensitive (Ts) phenotype of a S. cerevisiae hsf1 mutant. An O. parapolymorpha strain with an H221R mutation in the DBD domain of OpHsf1 exhibited significantly retarded growth and a Ts phenotype. Intriguingly, the expression of heat-shock-protein‒coding genes harboring HSEs was significantly decreased in the H221R mutant strain, even under non-stress conditions, indicating the importance of the DBD for the basal growth of O. parapolymorpha. Notably, even though the deletion of C-terminal domains (ΔCE2, ΔAR2, ΔCTM) of OpHsf1 destroyed complementation of the growth defect of the S. cerevisiae hsf1 strain, the C-terminal domains were shown to be dispensable in O. parapolymorpha. Overexpression of OpHsf1 in S. cerevisiae increased resistance to transient heat shock, supporting the idea that OpHsf1 could be useful in the development of heatshock‒ resistant yeast host strains.

Development of a strategy for the screening of α-glucosidase-producing microorganisms: Bo Zhou+ , Nan Huang+ , Wei Zeng+ , Hao Zhang , Guiguang Chen , Zhiqun Liang; J. Microbiol. 2020;58(2):163-172. Published online January 29, 2020; DOI: https://doi.org/10.1007/s12275-020-9267-4

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Abstract: α-Glucosidase is a crucial enzyme for the production of isomaltooligosaccharide. In this study, a novel method comprising eosin Y (EY) and α-D-methylglucoside (AMG) in glass plates was tested for the primary screening of α-glucosidaseproducing strains. First, α-glucosidase-producing Aspergillus niger strains were selected on plates containing EY and AMG based on transparent zone formation resulting from the solubilization of EY by the hydrolyzed product. Conventional
methods
that use trypan blue (TB) and p-nitrophenyl-α-Dglucopyranoside (pPNP) as indicators were then compared with the new strategy. The results showed that EY-containing plates provide the advantages of low price and higher specificity for the screening of α-glucosidase-producing strains. We then evaluated the correlation between the hydrolytic activity of α-glucosidase and diffusion distance, and found that good linearity could be established within a 6–75 U/ml enzyme concentration range. Finally, the hydrolytic and transglycosylation activities of α-glucosidase obtained from the target isolates were determined by EY plate assay and 3,5- dinitrosalicylic acid-Saccharomyces cerevisiae assay, respectively. The results showed that the diameter of the transparent zone varied among isolates was positively correlated with α-glucosidase hydrolytic activity, while good linearity could also be established between α-glucosidase transglycosylation activity and non-fermentable reducing sugars content. With this strategy, 7 Aspergillus niger mutants with high yield of α-glucosidase from 200 obvious single colonies on the primary screen plate were obtained.

Overexpression and characterization of a novel cold-adapted and salt-tolerant GH1 β-glucosidase from the marine bacterium Alteromonas sp. L82: Jingjing Sun , Wei Wang , Congyu Yao , Fangqun Dai , Xiangjie Zhu , Junzhong Liu , Jianhua Hao; J. Microbiol. 2018;56(9):656-664. Published online August 23, 2018; DOI: https://doi.org/10.1007/s12275-018-8018-2

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41 Citations

Abstract: A novel gene (bgl) encoding a cold-adapted β-glucosidase was cloned from the marine bacterium Alteromonas sp. L82. Based on sequence analysis and its putative catalytic conserved region, Bgl belonged to the glycoside hydrolase family 1. Bgl was overexpressed in E. coli and purified by Ni2+ affinity chromatography. The purified recombinant β- glucosidase showed maximum activity at temperatures between 25°C to 45°C and over the pH range 6 to 8. The enzyme lost activity quickly after incubation at 40°C. Therefore, recombinant β-glucosidase appears to be a cold-adapted enzyme. The addition of reducing agent doubled its activity and 2 M NaCl did not influence its activity. Recombinant β-glucosidase was also tolerant of 700 mM glucose and some organic solvents. Bgl had a Km of 0.55 mM, a Vmax of 83.6 U/mg, a kcat of 74.3 s-1 and kcat/Km of 135.1 at 40°C, pH 7 with 4-nitrophenyl-β-D-glucopyranoside as a substrate. These properties indicate Bgl may be an interesting candidate for biotechnological and industrial applications.

Diversity and enzyme activity of Penicillium species associated with macroalgae in Jeju Island: Myung Soo Park , Seobihn Lee , Seung-Yoon Oh , Ga Youn Cho , Young Woon Lim; J. Microbiol. 2016;54(10):646-654. Published online September 30, 2016; DOI: https://doi.org/10.1007/s12275-016-6324-0

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Abstract: A total of 28 strains of 19 Penicillium species were isolated in a survey of extracellular enzyme-producing fungi from macroalgae along the coast of Jeju Island of Korea. Penicillium species were identified based on morphological and β-tubulin sequence analyses. In addition, the halo-tolerance and enzyme activity of all strains were evaluated. The diversity of Penicillium strains isolated from brown algae was higher than the diversity of strains isolated from green and red algae. The commonly isolated species were Penicillium antarcticum, P. bialowiezense, P. brevicompactum, P. crustosum, P. oxalicum, P. rubens, P. sumatrense, and P. terrigenum. While many strains showed endoglucanase, β-glucosidase, and protease activity, no alginase activity was detected. There was a positive correlation between halo-tolerance and endoglucanase activity within Penicillium species. Among 19 Penicillium species, three species–P. kongii, P. olsonii, and P. viticola– have not been previously recorded in Korea.

Research Support, Non-U.S. Gov'ts

Characterization of Recombinant β-Glucosidase from Arthrobacter chlorophenolicus and Biotransformation of Ginsenosides Rb1, Rb2, Rc, and Rd: Myung Keun Park , Chang-Hao Cui , Sung Chul Park , Seul-Ki Park , Jin-Kwang Kim , Mi-Sun Jung , Suk-Chae Jung , Mi-Sun Jung , Suk-Chae Jung , Sun-Chang Kim , Wan-Taek Im; J. Microbiol. 2014;52(5):399-406. Published online May 9, 2014; DOI: https://doi.org/10.1007/s12275-014-3601-7

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Abstract: The focus of this study was the cloning, expression, and characterization of recombinant ginsenoside hydrolyzing β-glucosidase from Arthrobacter chlorophenolicus with an ultimate objective to more efficiently bio-transform ginse-nosides. The gene bglAch, consisting of 1,260 bp (419 amino acid residues) was cloned and the recombinant enzyme, over-expressed in Escherichia coli BL21 (DE3), was characterized. The GST-fused BglAch was purified using GST·Bind agarose resin and characterized. Under optimal conditions (pH 6.0 and 37°C) BglAch hydrolyzed the outer glucose and arabino-pyranose moieties of ginsenosides Rb1 and Rb2 at the C20 position of the aglycone into ginsenoside Rd. This was fol-lowed by hydrolysis into F2 of the outer glucose moiety of ginsenoside Rd at the C3 position of the aglycone. Additio-nally, BglAch more slowly transformed Rc to F2 via C-Mc1 (compared to hydrolysis of Rb1 or Rb2). These results in-dicate that the recombinant BglAch could be useful for the production of ginsenoside F2 for use in the pharmaceutical and cosmetic industries.

Identification of the Genes Involved in 1-Deoxynojirimycin Synthesis in Bacillus subtilis MORI 3K-85: Kyung-Don Kang , Yong Seok Cho , Ji Hye Song , Young Shik Park , Jae Yeon Lee , Kyo Yeol Hwang , Sang Ki Rhee , Ji Hyung Chung , Ohsuk Kwon , Su-Il Seong; J. Microbiol. 2011;49(3):431-440. Published online June 30, 2011; DOI: https://doi.org/10.1007/s12275-011-1238-3

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Abstract: 1-Deoxynojirimycin (DNJ), a D-glucose analogue with a nitrogen atom substituting for the ring oxygen, is a strong inhibitor of intestinal α-glucosidase. DNJ has several promising biological activities, including its antidiabetic, antitumor, and antiviral activities. Nevertheless, only limited amounts of DNJ are available because it can only be extracted from some higher plants, including the mulberry tree, or purified from the culture broth of several types of soil bacteria, such as Streptomyces sp. and Bacillus sp. In our previous study, a DNJ-producing bacterium, Bacillus subtilis MORI, was isolated from the traditional Korean fermented food Chungkookjang. In the present study, we report the identification of the DNJ biosynthetic genes in B. subtilis MORI 3K-85 strain, a DNJ-overproducing derivate of the B. subtilis MORI strain generated by γ-irradiation. The genomic DNA library of B. subtilis MORI 3K-85 was constructed in Escherichia coli, and clones showing α-glucosidase inhibition activity were selected. After DNA sequencing and a series of subcloning, we were able to identify a putative operon which consists of gabT1, yktc1, and gutB1 genes predicted to encode putative transaminase, phosphatase, and oxidoreductase, respectively. When a recombinant plasmid containing this operon sequence was transformed into an E. coli strain, the resulting transformant was able to produce DNJ into the culture medium. Our results indicate that the gabT1, yktc1, and gutB1 genes are involved in the DNJ biosynthetic pathway in B. subtilis MORI, suggesting the possibility of employing these genes to establish a large-scale microbial DNJ overproduction system through genetic engineering and process optimization.

Identification and Functional Analysis of a Gene Encoding β-Glucosidase from the Brown-Rot Basidiomycete Fomitopsis palustris: Hwang-Woo Ji , Chang-Jun Cha; J. Microbiol. 2010;48(6):808-813. Published online January 9, 2011; DOI: https://doi.org/10.1007/s12275-010-0482-2

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Abstract: The brown-rot basidiomycete Fomitopsis palustris is known to degrade crystalline cellulose (Avicel) and produce three major cellulases, exoglucanases, endoglucanases, and β-glucosidases. A novel β-glucosidase designated as Cel3A was identified from F. palustris grown at the expense of Avicel. The deduced amino acid sequence of Cel3A showed high homology with those of other fungal β-glucosidases that belong to glycosyl hydrolase (GH) family 3. The sequence analysis also indicated that Cel3A contains the N- and C-terminal domains of GH family 3 and Asp-209 was conserved as a catalytic nucleophile. The cloned gene was successfully expressed in the yeast Pichia pastoris and the recombinant protein exhibited β-glucosidase activity with cellobiose and some degree of thermostability. Considering the size and sequence of the protein, the β-glucosidase identified in this study is different from the protein purified directly from F. palustris in the previous study. Our results suggest that the fungus possesses at least two β-glucosidase genes.

Purification and Characterization of the α-Glucosidase Produced by Thermophilic Fungus Thermoascus aurantiacus CBMAI 756: Ana Flávia Azevedo Carvalho , Maurício Boscolo , Roberto da Silva , Henrique Ferreira , Eleni Gomes; J. Microbiol. 2010;48(4):452-459. Published online August 20, 2010; DOI: https://doi.org/10.1007/s12275-010-9319-2

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Abstract: Αn α-glucosidase enzyme produced by the fungus Thermoascus aurantiacus CBMAI 756 was purified by ultra filtration, ammonium sulphate precipitation, and chromatography using Q Sepharose, Sephacryl S-200, and Superose 12 columns. The apparent molecular mass of the enzyme was 83 kDa as determined in gel electrophoresis. Maximum activity was observed at pH 4.5 at 70°C. Enzyme showed stability stable in the pH range of 3.0-9.0 and lost 40% of its initial activity at the temperatures of 40, 50, and 60°C. In the presence of ions Na+, Ba2+, Co2+, Ni2+, Mg2+, Mn2+, Al3+, Zn2+, Ca2+ this enzyme maintained 90-105% of its maximum activity and was inhibited by Cr3+, Ag+, and Hg2+. The enzyme showed a transglycosylation property, by the release of oligosaccharides after 3 h of incubation with maltose, and specificity for short maltooligosaccharides and α-PNPG. The Km measured for the α-glucosidase was 0.07 μM, with a Vmax of 318.0 μmol/min/mg.

Purification and Biochemical Properties of a Glucose-Stimulated β-D-Glucosidase Produced by Humicola grisea var. thermoidea Grown on Sugarcane Bagasse: Cesar Vanderlei Nascimento , Flávio Henrique Moreira Souza , Douglas Chodi Masui , Francisco Assis Leone , Rosane Marina Peralta , João Atílio Jorge , Rosa Prazeres Melo Furriel; J. Microbiol. 2010;48(1):53-62. Published online March 11, 2010; DOI: https://doi.org/10.1007/s12275-009-0159-x

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Abstract: The effect of several carbon sources on the production of mycelial-bound β-glucosidase by Humicola grisea var. thermoidea in submerged fermentation was investigated. Maximum production occurred when cellulose was present in the culture medium, but higher specific activities were achieved with cellobiose or sugarcane bagasse. Xylose or glucose (1%) in the reaction medium stimulated β-glucosidase activity by about 2-fold in crude extracts from mycelia grown in sugarcane bagasse. The enzyme was purified by ammonium sulfate precipitation, followed by Sephadex G-200 and DEAE-cellulose chromatography, showing a single band in PAGE and SDS-PAGE. The β-glucosidase had a carbohydrate content of 43% and showed apparent molecular masses of 57 and 60 kDa, as estimated by SDS-PAGE and gel filtration, respectively. The optimal pH and temperature were 6.0 and 50°C, respectively. The purified enzyme was thermostable up to 60 min in water at 55°C and showed half-lives of 7 and 14 min when incubated in the absence or presence of 50 mM glucose, respectively, at 60°C. The enzyme hydrolyzed p-nitrophenyl-β-D-glucopyranoside, p-nitrophenyl-β-galactopyranoside, p-nitrophenyl-β-D-fucopyranoside, p-nitrophenyl-β-D-xylopyranoside, o-nitrophenyl-β-Dgalactopyranoside, lactose, and cellobiose. The best synthetic and natural substrates were p-nitrophenyl-β-Dfucopyranoside and cellobiose, respectively. Purified enzyme activity was stimulated up to 2-fold by glucose or xylose at concentrations from 25 to 200 mM. The addition of purified or crude β-glucosidase to a reaction medium containing Trichoderma reesei cellulases increased the saccharification of sugarcane bagasse by about 50%. These findings suggest that H. grisea var. thermoidea β-glucosidase has a potential for biotechnological applications in the bioconversion of lignocellulosic materials.

Characterization of a Novel β-Glucosidase-Like Activity from a Soil Metagenome: Chengjian Jiang , Gefei Ma , Shuangxi Li , Tingting Hu , Zhiqun Che , Peihong Shen , Bing Yan , Bo Wu; J. Microbiol. 2009;47(5):542-548. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-009-0024-y

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Abstract: We report the cloning of a novel β-glucosidase-like gene by function-based screening of a metagenomic library from uncultured soil microorganisms. The gene was named bgl1C and has an open reading frame of 1,443 base pairs. It encodes a 481 amino acid polypeptide with a predicted molecular mass of about 57.8 kDa. The deduced amino acid sequence did not show any homology with known β-glucosidases. The putative β-glucosidase gene was subcloned into the pETBlue-2 vector and overexpressed in E. coli Tuner (DE3) pLacІ; the recombinant protein was purified to homogeneity. Functional characterization with a high performance liquid chromatography method demonstrated that the recombinant Bgl1C protein hydrolyzed D-glucosyl-β-(1-4)-D-glucose to glucose. The maximum activity for Bgl1C protein occurred at pH 8.0 and 42°C using p-nitrophenyl-β-D-glucoside as the substrate. A CaCl2 concentration of 1 mM was required for optimal activity. The putative β-glucosidase had an apparent Km value of 0.19 mM, a Vmax value of 4.75 U/mg and a kcat value of 316.7/min under the optimal reaction conditions. The biochemical characterization of Bgl1C has enlarged our understanding of the novel enzymes that can be isolated from the soil metagenome.

A Specific Short Dextrin-Hydrolyzing Extracellular Glucosidase from the Thermophilic Fungus Thermoascus aurantiacus 179-5: Ana Flavia Azevedo Carvalho , Aline Zorzetto Gonclves , Roberto da Silva , Eleni Gomes; J. Microbiol. 2006;44(3):276-283.; DOI: https://doi.org/2385 [pii]

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Abstract: The thermophilic fungus Thermoascus aurantiacus 179-5 produced large quantities of a glucosidase which preferentially hydrolyzed maltose over starch. Enzyme production was high in submerged fermentation, with a maximal activity of 30 U/ml after 336 h of fermentation. In solid-state fermentation, the activity of the enzyme was 22 U/ml at 144 h in medium containing wheat bran and 5.8 U/ml at 48 h when cassava pulp was used as the culture medium. The enzyme was specific for maltose, very slowly hydrolyzed starch, dextrins (2-7G) and the synthetic substrate (α-PNPG), and did not hydrolyze sucrose. These properties suggest that the enzyme is a type II α-glucosidase. The optimum temperature of the enzyme was 70?. In addition, the enzyme was highly thermostable (100% stability for 10 h at 60? and a half-life of 15 min at 80?), and stable within a wide pH range.

Degradation of Crystalline Cellulose by the Brown-rot Basidiomycete Fomitopsis palustris: Jeong-Jun Yoon , Young-Kyoon Kim; J. Microbiol. 2005;43(6):487-492.; DOI: https://doi.org/2301 [pii]

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Abstract: This study demonstrated that the brown rot basidiomycete Fomitopsis palustris was able to degrade crystalline cellulose (Avicel). This fungus could also produce the three major cellulases (exoglucanases, endoglucanases, and -glucosidase) when the cells were grown on 2.0% Avicel. Avicel degraded by F. palustris showed a decrease in relative crystallinity from 83% to 78.5% after 14 days of incubation. The characterization study indicated that optimum pH was 4.5 and optimum temperature was 70oC for exoglucanase (cellobiohydrolase) activity. Hydrolysis of Avicel by the crude enzyme from F. palustris yielded 1.6 mg/ml of glucose after 43 h, which corresponded to a cellulose conversion degree of 3.2%. Therefore, this study revealed for the first time that the brown rot basidiomycete F. palustris produces cellulases capable of yielding soluble sugars from crystalline cellulose.

Journal Articles

Molecular Detection of [alpha]-Glucosidase Inhibitor-producing Actinomycetes: Chang-Gu Hyun , Seung-Young Kim , Jin-Haeng Hur , Myung-Ji Seo , Joo-Won Suh , Soon-Ok Kim; J. Microbiol. 2005;43(3):313-318.; DOI: https://doi.org/2207 [pii]

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Abstract: In this study, we demonstrate the use of a PCR-based method for the detection of the specific genes involved in natural-product biosynthesis. This method was applied, using specifically designed PCR primers, to the amplification of a gene segment encoding for sedo-heptulose 7-phosphate cyclase, which appears to be involved in the biosynthetic pathways of C_7N aminoacyclitol or its keto analogue-containing metabolites, in a variety of actinomycetes species. The sequences of DNA fragments (about 540 bp) obtained from three out of 39 actinomycete strains exhibited a high degree of homology with the sedo-heptulose 7-phosphate cyclase gene, which has been implicated in acarbose biosynthesis. The selective cultivation conditions of this experiment induced the expression of these loci, indicating that the range of C_7N aminoacyclitol or its keto analogue-group natural products might be far greater than was previously imagined. Considering that a total of approximately 20 C_7N aminoacyclitol metabolites, or its keto analogue-containing metabolites, have been described to date, it appears likely that some of the unknown loci described herein might constitute new classes of C_7N aminoacyclitol, or of its keto analogue-containing metabolites. As these metabolites, some of which contain valienamine, are among the most potent antidiabetic agents thus far discovered, the molecular detection of specific metabolite-producing actinomycetes may prove a crucial step in current attempts to expand the scope and diversity of natural-product discovery.

Isolation and Characterization of a-Glucosidase Inhibitor from the Fungus Ganoderma lucidum: Shin-Duk Kim , Hong Joon Nho; J. Microbiol. 2004;42(3):223-227.; DOI: https://doi.org/2085 [pii]

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Abstract: An [alpha]-glucosidase inhibitor, SKG-3, was isolated from the fruiting bodies of Ganoderma lucidum and its physico-chemical properties were characterized. It was a highly specific and effective reversible inhibitor of [alpha]-glucosidase. It showed very potent inhibitory activity against [alpha]-glucosidase with an IC_50 value of 4.6 mg/ml, but no activity for any other glycosidases tested. Enzyme activity could be recovered upon dialysis, thus providing evidence for the reversibility of the inhibition. A Lineweaver-Burk plot indicated that the SKG-3 inhibition of [alpha]-glucosidase was competitive.

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