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Kishimoto T, Hori H, Takano D, Nakano Y, Watanabe M, Mitsui T. Rice alpha-mannosidase digesting the high mannose glycopeptide of glutelin. PHYSIOLOGIA PLANTARUM 2001; 112:15-24. [PMID: 11319010 DOI: 10.1034/j.1399-3054.2001.1120103.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
alpha-Mannosidase (EC 3.2.1.24) from rice dry seeds was purified to homogeneity. Optimum pH and Km for pNP-alpha-Man hydrolysis were pH 4.3-4.5 and 1.04 mM, respectively. The enzyme digested mannobioses such as Manalpha-1,2Man, Manalpha-1,6Man, Manalpha-1,3Man but Manalpha-1,4Man. Zn2+ ion was required for the activity, whereas EDTA and swainsonine inhibited the activity by 80 and 96%, respectively. The rice storage protein, glutelin was prepared and its basic subunits were shown to have high mannose-type sugar chains by two-dimensional mapping using NH2-P and C18 silica columns. They were Man9GlcNAc2, Man8GlcNAc2, Man7GlcNAc2, Man6GlcNAc2 and Man5GlcNAc2. All these oligosaccharides were digested by the purified alpha-mannosidase, and Man-GlcNAc2 and mannose were formed. Glycopeptides, having these high mannose-type sugar chains, could also be digested by the alpha-mannosidase. Subunits were prepared from glutelin basic subunit and the richest subunit among them, subunit 2 (isoform 2), was digested by the alpha-mannosidase. Isoform 2 was digested by V8 protease only partially and slowly. However, isoform 2, pre-treated with the alpha-mannosidase, was rapidly and completely digested by V8 protease.
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Affiliation(s)
- Tadashi Kishimoto
- Graduate School of Natural Science and Technology, Niigata University, Ikarashi, Niigata 950-2181, Japan
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52
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Rivera-Marrero CA, Ritzenthaler JD, Roman J, Moremen KW. Molecular cloning and expression of an alpha-mannosidase gene in Mycobacterium tuberculosis. Microb Pathog 2001; 30:9-18. [PMID: 11162181 DOI: 10.1006/mpat.2000.0407] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mannose is a major component of glycolipids and glycoproteins of the cell envelope of M. tuberculosis (Mtb). However, the enzymes involved in the biosynthesis and catabolism of mannosylated glycans are largely unknown. We demonstrate alpha-mannosidase activity towards the fluorescent substrate 4-methylumberlliferyl-alpha-D-mannopyranoside (4MU-Man) in cell lysates of attenuated and virulent Mtb bacilli, with two-fold higher activity in the virulent strain Erdman. Mannosidase activity was optimal at pH 6.5, was not inhibited by deoxymannojirimycin (dMNJ), was mildly inhibited by swainsonine (SW) and stimulated two-fold by EDTA. GenBank BLAST analysis for sequences homologous to eukaryotic alpha-mannosidases revealed a 3.6 kb putative gene (Rv0648) in Mtb cosmid SCY20H10 (Acc# z92772), with strong homology (48%) to the rat ER/cytosolic alpha-mannosidase and containing signature sequences of class 2 mannosidases. By RT-PCR, gene Rv0648 was found differentially expressed, with lower expression during growth in A549 pneumocyte cultures. Gene Rv0648 was cloned, expressed in E. coli, and alpha-mannosidase activity in cell lysates determined. Expression of alphaMan-pET in E. coli cells resulted in an eight-fold increase in mannosidase activity toward 4-MU-Man, upon IPTG induction. Partial purification of the histidine-tagged Mtb mannosidase by metal chelation affinity chromatography, and analysis by SDS-PAGE, showed a protein with the predicted m.w. of 137.5 kDa. Enzyme assays of the column fractions showed alpha-mannosidase activity toward synthetic aryl-mannose substrates, in fractions enriched in the recombinant Mtb mannosidase. These results demonstrate that gene Rv0648 encodes an active alpha-mannosidase in Mtb.
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Affiliation(s)
- C A Rivera-Marrero
- Department of Medicine, Emory University School of Medicine, Decatur, GA 30033, USA.
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Fujiyama K, Kira Y, Iizuka M, Kimura Y, Seki T. Identification of putative gene encoded on ORF16 of the 81 kb contig of Arabidopsis thaliana chromosome III as α-mannosidase. J Biosci Bioeng 2001. [DOI: 10.1016/s1389-1723(01)80248-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Ly HD, Howard S, Shum K, He S, Zhu A, Withers SG. The synthesis, testing and use of 5-fluoro-alpha-D-galactosyl fluoride to trap an intermediate on green coffee bean alpha-galactosidase and identify the catalytic nucleophile. Carbohydr Res 2000; 329:539-47. [PMID: 11128583 DOI: 10.1016/s0008-6215(00)00214-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
5-Fluoro-alpha-D-galactopyranosyl fluoride was synthesized and its interaction with the active site of an alpha-galactosidase from green coffee bean (Coffea arabica), a retaining glycosidase, characterized kinetically and structurally. The compound behaves as an apparently tight binding (Ki = 600 nM) competitive inhibitor, achieving this high affinity through reaction as a slow substrate that accumulates a high steady-state concentration of the glycosyl-enzyme intermediate, as evidenced by ESiMS. Proteolysis of the trapped enzyme coupled with HPLC/MS analysis allowed the localization of a labeled peptide that was subsequently sequenced. Comparison of this sequence information to that of other members of the same glycosidase family revealed the active site nucleophile to be Asp145 within the sequence LKYDNCNNN. The importance of this residue to catalysis has been confirmed by mutagenesis studies.
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Affiliation(s)
- H D Ly
- Department of Chemistry, University of British Columbia, Vancouver, BC, Canada
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55
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Numao S, He S, Evjen G, Howard S, Tollersrud OK, Withers SG. Identification of Asp197 as the catalytic nucleophile in the family 38 alpha-mannosidase from bovine kidney lysosomes. FEBS Lett 2000; 484:175-8. [PMID: 11078873 DOI: 10.1016/s0014-5793(00)02148-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Bovine kidney lysosomal alpha-mannosidase is a family 38 alpha-mannosidase involved in the degradation of glycoproteins. The mechanism-based reagent, 5-fluoro-beta-L-gulosyl fluoride, was used to trap a glycosyl-enzyme intermediate, thereby labelling the catalytic nucleophile of this enzyme. After proteolytic digestion and high performance liquid chromatography/tandem mass spectrometry (MS) analysis, a labelled peptide was localised, and the sequence: HIDPFGHSRE determined by fragmentation tandem MS analysis. Taking into consideration sequence alignments of this region with those of other alpha-mannosidases of the same family, this result strongly suggests that the catalytic nucleophile in this enzyme is Asp197.
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Affiliation(s)
- S Numao
- Department of Chemistry, University of British Columbia, Vancouver, Canada
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56
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Hart DO, He S, Chany CJ, Withers SG, Sims PF, Sinnott ML, Brumer H. Identification of Asp-130 as the catalytic nucleophile in the main alpha-galactosidase from Phanerochaete chrysosporium, a family 27 glycosyl hydrolase. Biochemistry 2000; 39:9826-36. [PMID: 10933800 DOI: 10.1021/bi0008074] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Characterization of the complete gene sequence encoding the alpha-galactosidase from Phanerochaete chrysosporium confirms that this enzyme is a member of glycosyl hydrolase family 27 [Henrissat, B., and Bairoch, A. (1996) Biochem. J. 316, 695-696]. This family, together with the family 36 alpha-galactosidases, forms glycosyl hydrolase clan GH-D, a superfamily of alpha-galactosidases, alpha-N-acetylgalactosaminidases, and isomaltodextranases which are likely to share a common catalytic mechanism and structural topology. Identification of the active site catalytic nucleophile was achieved by labeling with the mechanism-based inactivator 2',4', 6'-trinitrophenyl 2-deoxy-2,2-difluoro-alpha-D-lyxo-hexopyranoside; this inactivator was synthesized by anomeric deprotection of the known 1,3,4,6-tetra-O-acetyl-2-deoxy-2, 2-difluoro-D-lyxo-hexopyranoside [McCarter, J. D., Adam, M. J., Braun, C., Namchuk, M., Tull, D., and Withers, S. G. (1993) Carbohydr. Res. 249, 77-90], picrylation with picryl fluoride and 2, 6-di-tert-butylpyridine, and O-deacetylation with methanolic HCl. Enzyme inactivation is a result of the formation of a stable 2-deoxy-2,2-difluoro-beta-D-lyxo-hexopyranosyl-enzyme intermediate. Following peptic digestion, comparative liquid chromatographic/mass spectrometric analysis of inactivated and control enzyme samples served to identify the covalently modified peptide. After purification of the labeled peptide, benzylamine was shown to successfully replace the 2-deoxy-2,2-difluoro-D-lyxo-hexopyranosyl peptidyl ester by aminolysis. The labeled amino acid was identified as Asp-130 of the mature protein by further tandem mass spectrometric analysis of the native and derivatized peptides in combination with Edman degradation analysis. Asp-130 is found within the sequence YLKYDNC, which is highly conserved in all known family 27 glycosyl hydrolases.
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Affiliation(s)
- D O Hart
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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57
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Abstract
Glycosyl fluorides have considerable importance as substrates and inhibitors in enzymatic reactions. Their good combination of stability and reactivity has enabled their use as glycosyl donors with a variety of carbohydrate processing enzymes. Moreover, the installation of fluorine elsewhere on the carbohydrate scaffold commonly modifies the properties of the glycosyl fluoride such that the resultant compounds act as slow substrates or even inhibitors of enzyme action. This review covers the use of glycosyl fluorides as substrates for wild-type and mutant glycosidases and other enzymes that catalyze glycosyl transfer. The use of substituted glycosyl fluorides as inhibitors of enzymes that catalyze glycosyl transfer and as tools for investigation of their mechanism is discussed, including the labeling of active site residues. Synthetic applications in which glycosyl fluorides are used as glycosyl donors in enzymatic transglycosylation reactions for the synthesis of oligo- and polysaccharides are then covered, including the use of mutant glycosidases, the so-called glycosynthases, which are able to catalyze the formation of glycosides without competing hydrolysis. Finally, a short overview of the use of glycosyl fluorides as substrates and inhibitors of phosphorylases and phosphoglucomutase is given.
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Affiliation(s)
- S J Williams
- Department of Chemistry, University of British Columbia, Vancouver, Canada
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58
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Cho SJ, Ling R, Kim A, Mariano PS. A versatile approach to the synthesis of (+)-mannostatin A analogues. J Org Chem 2000; 65:1574-7. [PMID: 10814128 DOI: 10.1021/jo991539m] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S J Cho
- Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 87131, USA
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59
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Vocadlo DJ, Mayer C, He S, Withers SG. Mechanism of action and identification of Asp242 as the catalytic nucleophile of Vibrio furnisii N-acetyl-beta-D-glucosaminidase using 2-acetamido-2-deoxy-5-fluoro-alpha-L-idopyranosyl fluoride. Biochemistry 2000; 39:117-26. [PMID: 10625486 DOI: 10.1021/bi991958d] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The novel mechanism-based reagent 2-acetamido-2-deoxy-5-fluoro-alpha-L-idopyranosykl fluoride has been synthesized, and the kinetic parameters K(M) = 0.23 mM and K(CAT)= 0.55 min(-1) for its hydrolysis by vibrio furnisi beta-N-acetylglucosaminidase (ExoII) HAVE been determined. Investigation of mixtures of enzyme with this slow substrate by electrospray mass spectrometry revealed a high steady-state population of the 2-acetamido-2-deoxy-5-fluoro-beta-L-idopyranosyl-enzyme, indicating that the hydrolytic mechanism of ExoII involves the formation and rate-determining hydrolysis of a glycosyl-enzyme intermediate. Analysis of a peptic digest of the glycosyl-enzyme by HPLC/ESMS/MS in the netural-loss mode permitted identification of a peptide bearing the 5-fluoro-sugar moiety. Tandem MS sequencing of the labeled peptide, in conjuction with multiple sequence alignmentsS of family 3 members, allowed the identification of ASP242 as the catalytic nucleophile within the sequence IVFSDDLSM.
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Affiliation(s)
- D J Vocadlo
- Protein Engineering Network of Centres of Excellence of Canada, Department of Chemistry, University of British Columbia, Vancouver
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60
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Zechel DL, He S, Dupont C, Withers SG. Identification of Glu-120 as the catalytic nucleophile in Streptomyces lividans endoglucanase celB. Biochem J 1998; 336 ( Pt 1):139-45. [PMID: 9806895 PMCID: PMC1219852 DOI: 10.1042/bj3360139] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Streptomyces lividans CelB is a family-12 endoglucanase that hydrolyses cellulose with retention of anomeric configuration. A recent X-ray structure of the catalytic domain at 1.75 A resolution has led to the preliminary assignment of Glu-120 and Glu-203 as the catalytic nucleophile and general acid-base respectively [Sulzenbacher, Shareck, Morosoli, Dupont and Davies (1997) Biochemistry 36, 16032-16039]. The present study confirms the identity of the nucleophile by trapping the glycosyl-enzyme intermediate with the mechanism-based inactivator 2', 4'-dinitrophenyl 2-deoxy-2-fluoro-beta-D-cellobioside (2FDNPC). The kinetics of inactivation proceeded in a saturable fashion, yielding the parameters kinact=0.29+/-0.02 min-1 and Kinact=0.72+/-0.08 mM. Uncompetitive inhibition was observed at high concentrations of 2FDNPC (Ki=9+/-1 mM), a behaviour that was also observed with the substrate 2',4'-dinitrophenyl beta-D-cellobioside (kcat=40+/-1 s-1, Km=0.35+/-0.03 mM, Ki=24+/-4 mM). Protection against inactivation was afforded by the competitive inhibitor cellobiose. The electrospray ionization (ESI) mass spectrum of the intact labelled CelB indicated that the inactivator had labelled the enzyme stoichiometrically. Reactivation of the trapped intermediate occurred spontaneously (kH2O=0.0022 min-1) or via transglycosylation, with cellobiose acting as an acceptor ligand (kreact=0.024 min-1, Kreact=54 mM). Digestion of the labelled enzyme by pepsin followed by LC-ESI-tandem MS (MS-MS) operating in neutral loss mode identified a labelled, singly charged peptide of m/z 947.5 Da. Isolation of this peptide by HPLC and subsequent collision-induced fragmentation by ESI-MS-MS produced a daughter-ion spectrum that corresponded to a sequence (QTEIM) containing Glu-120. The nucleophile Glu-120 and the putative acid-base catalyst Glu-203 are conserved in all known family-12 sequences.
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Affiliation(s)
- D L Zechel
- Department of Chemistry, University of British Columbia, Vancouver, 2036 Main Mall, Vancouver, British Columbia, Canada, V6T 1Z1
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61
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Howard S, Withers SG. Labeling and identification of the postulated acid/base catalyst in the alpha-glucosidase from Saccharomyces cerevisiae using a novel bromoketone C-glycoside. Biochemistry 1998; 37:3858-64. [PMID: 9521706 DOI: 10.1021/bi9727085] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
alpha-Glucosidase from Saccharomyces cerevisiae is a member of a sequence-related family of alpha-glycosidases (family 13) that includes digestive alpha-amylases and commercially important cyclodextrin glucanotransferases. These enzymes catalyze the hydrolysis of alpha-linked oligosaccharides by a two-step mechanism involving a glycosyl-enzyme intermediate. A novel bromoketone C-glycoside inactivator, 1'-bromo-3'-(alpha-D-mannopyranosyl)-2'-propanone, has been synthesized and used to label the putative acid/base catalyst (Glu-276) of yeast alpha-glucosidase. Electrospray ionization mass spectrometry was used to demonstrate stoichiometric labeling of the protein. The labeled residue was identified by comparative liquid chromatographic/mass spectrometric analysis of peptic digests of labeled and unlabeled enzyme samples, which confirmed the unique presence of two labeled peptides of m/z 745 and 694. Subsequent tandem mass spectrometric analysis in the daughter-ion scan mode showed the two peptides to have an overlapping sequence in which Glu-276 was the labeled residue. Together with active-site-directed protection against inactivation with deoxynojirimycin, these results prove that Glu-276 is located within the active site of yeast alpha-glucosidase and, thus, provide further evidence for this residue playing an important role in catalysis.
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Affiliation(s)
- S Howard
- Protein Engineering Network of Centres of Excellence of Canada, Vancouver, British Columbia
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