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Query: EC:3.2.1.21 (beta-glucosidase)
 3,280 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new type of glycopeptidase hydrolyzing beta-aspartylglycosylamine linkages was partially purified from almond emulsin by chromatography on Sephadex G-200 and DE 52. The enzyme degraded stem bromelain glycopeptide, Asn-Asn(Man3,Xyl1,Fuc1,GlcNAc2)-Glu-Ser-Ser, to yield equimolar amounts of intact oligosaccharide, peptide (Asn-Asp-Glu-Ser-Ser), and ammonia. The Km value for the stem bromelain glycopeptide was 4 mM, and the optimum pH was 5.2. The enzyme was markedly inhibited by 10 mM Cu2+, Fe3+, and Zn2+. Thiol inhibitors and actinomycete protease inhibitors had no effect. The glycopeptides used as substrates were prepared from stem bromelain, ovalbumin or ovotransferrin. The enzyme hydrolyzed glycopeptides with 3-11 amino acid residues, whereas it did not hydrolyze glycopeptides with 1-2 amino acid residues. Furthermore, Asn-oligosaccharide was not inhibitory to the enzyme.
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PMID:Some characteristics of a new glycopeptidase acting on aspartylglycosylamine linkages. 73 97

A comparative study was undertaken to characterize the linkages of L-fucose in N-glycans of plasma membrane glycoproteins from Morris hepatoma 7777, host liver and kidney cortex, as well as from rat serum. After in-vivo radiolabelling of rats with L-[6-3H]fucose, the asparagine-linked carbohydrate chains were released from delipidated plasma membrane glycoproteins, as well as from serum glycoproteins, by enzymic digestion with peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase from Flavobacterium meningosepticum. They were then converted to their corresponding oligosaccharide alditols by reduction with sodium borohydride. Two specific alpha-L-fucosidases from almond emulsin and from Aspergillus niger, combined with affinity HPLC on immobilized Aleuria aurantia lectin were used to study the linkage of L-fucose in the oligosaccharide chains. Fucose alpha 1-2 linked to galactose, was present only in the plasma membrane of hepatoma 7777 (18% of total L-[3H]fucose in N-glycans), but was not expressed in host liver, kidney cortex and serum. None of the investigated sources contained an appreciable amount of fucose alpha 1-3/4 linked to N-acetyl-D-glucosamine. All the radioactively labelled oligosaccharides from host liver, kidney cortex and serum, but only 82% of these oligosaccharides from hepatoma, contained alpha-fucosyl residues linked at the C6 position of the proximal N-acetyl-D-glucosamine.
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PMID:Occurrence of alpha 1-2-fucosylation in membrane glycoproteins of Morris hepatoma 7777 but not in liver. Aberrant type of fucosylation in a malignant tissue. 139 74

Two beta-glucosidases (I and II) were isolated from Schizophyllum commune, and their physical and chemical properties studied. The two enzymes have very similar sequences, as shown by HPLC analysis of tryptic digests and partial amino acid sequencing. As judged by their circular dichroism spectra, they have almost identical secondary structure. The estimates for alpha-helix, beta-sheet, and other structures were 21%, 40% and 39%, respectively, for beta-glucosidase I and 27%, 32% and 41% for beta-glucosidase II. Their near-ultraviolet spectra were identical. beta-Glucosidase I was more highly glycosylated than beta-glucosidase II, having 2 mol N-acetylglucosamine/mol enzyme 36, mol mannose/mol enzyme and 1.2 mol glucose/mol enzyme vs 1.2, 17 and 3 mol/mol, respectively, in beta-glucosidase II. The native glycosylated form of beta-glucosidase I had a molecular mass of 102 kDa, and that of beta-glucosidase II, 96 kDa. As estimated from sensitivity to N-glycanase, beta-glucosidase II sugars were mainly asparagine linked, but much of the sugar in beta-glucosidase I was not removed by this treatment and was apparently serine or threonine linked. Kinetic analysis showed that both forms had similar Km values (0.3-2.1 mM) for oligosaccharides of 2-6 residues, but the kcat values of beta-glucosidase II were lower by 30-75% than those of beta-glucosidase I. The substrate dependence of kcat/Km indicated that both enzymes had binding sites for three glucose residues. The pH optimum of beta-glucosidase I was higher than that of beta-glucosidase II (5.8 vs 5.1). Both had similar specificities for several (R)-beta-D-glucosides tested. Both enzymes were competitively inhibited by their glucose product, but beta-glucosidase II was consistently less inhibited than beta-glucosidase I. Cellobiase activity was much more markedly inhibited than the activity with higher oligosaccharides, and the result of this, plus the lower hydrolytic rate with cellobiose, resulted in an accumulation of cellobiose as higher oligosaccharides were digested. Glucono-delta-lactone inhibited both enzymes and the hydrolysis of all oligosaccharide substrates similarly (Ki = 4 microM). We conclude that the catalytic site is identical in both enzymes, but subtle structural differences are reflected in a differential activity on the higher oligosaccharides and in the differential effects of the glucose product as an inhibitor. Furthermore, ethanol had a stimulatory effect on beta-glucosidase I but inhibited beta-glucosidase II, which presumably reflects differential effects of ethanol on the conformations of the two species.
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PMID:Kinetics and specificities of two closely related beta-glucosidases secreted by Schizophyllum commune. 211 5

A sialoglycoprotein, an integral component of the head plasma membrane of human spermatozoa, is recognized by the a-HS 1A.1 monoclonal antibody. The antigenicity is associated with the sugar moiety since: a) trypsin digestion did not affect the antigenic determinant; b) pretreatment of the cells with beta-glucosidase, alpha-mannosidase and neuraminidase completely abolished antibody binding. Endoglycosidase D and glycopeptidase F were inactive. The a-HS 1A.1 did not recognize a variety of blood-group related synthetic oligosaccharides. The species specificity was studied by indirect immunofluorescence assay. The antibody also recognized an antigen on Macaca fascicularis sperm, but failed to bind to spermatozoa of boar, bull, goat, ram, stallion, dog, rabbit, rooster, carp and eel.
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PMID:Primate specific sialoglycoprotein of sperm head plasma membrane defined by an anti-carbohydrate monoclonal antibody. 331 19

The glycopeptidase preparation that has been isolated from almond emulsin and acts on beta-aspartylglycosylamine linkages in glycopeptides was separated into three active fractions by DEAE-cellulose column chromatography. The three discrete species of glycopeptidase (Groups A, B and C) have been purified 30-, 136-, and 99-fold, respectively. The optimum pH value of Group A was 6.0 and those of Groups B and C, 5.0. Isoelectric points of Groups A, B and C were pH 7.7, 8.6 and 8.7, respectively. All three glycopeptidases hydrolyzed quantitatively glycopeptides with 3-11 amino acid residues prepared from stem bromelain, ovalbumin and ovotransferrin. Group C preferred glycopeptides with shorter peptide chains, whereas Groups A and B preferred those with longer chains. Glycopeptidase Group A also hydrolyzed intact glycoproteins such as stem bromelain, ovalbumin, Taka-amylase A and desialylated human transferrin.
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PMID:Almond glycopeptidase acting on aspartylglycosylamine linkages. Multiplicity and substrate specificity. 721 57

Glycoamidases (peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase, EC 3.5.1.52; also known as peptide: N-glycanases (PNGases) release N-linked oligosaccharides from glycopeptides and/or glycoproteins by hydrolyzing the glycosylated beta-amide bond of the asparagine side chain. The most widely used glycoamidases are those from Flavobacterium meningosepticum (glycoamidase F or PNGase F) and almond emulsin (glycoamidase A or PNGase A). To study the substrate structure requirement of these enzymes systematically, we synthesized >30 glycopeptides containing cellobiose, lactose, GlcNAc, and di-N,N'-acetylchitobiose (CTB). The length of the peptide was varied from one to five amino acids, and glycosylamines were linked to either Asn or Gln located at different positions in the peptide, including NH2 and COOH termini. Neither enzyme could cleave cellobiose and lactose glycopeptides, indicating that the 2-acetamido group on the Asn-linked GlcNAc is important in the recognition by both glycoamidases A and F. GlcNAc peptides could be cleaved by both enzymes, albeit not as effectively as CTB glycopeptides. Neither enzyme requires the Asn-Xaa-(Ser/Thr) sequence (required for N-glycosylation) for activity. Glycoamidase A could even hydrolyze a Gln-bound CTB glycopeptide, whereas the action of glycoamidase F on this substrate is minimal. While glycoamidase A could act on CTB dipeptides, glycoamidase F preferred a tripeptide or longer. The Km and Vmax values of glycoamidase A for t-butoxycarbonyl-(CTB)-Asn-Ala-Ser-OMe were 2.1 mM and 0.66 micromol/min/mg, respectively. A natural glycodipeptide, Man9-GlcNAc2-Asn-Phe, was also completely hydrolyzed by glycoamidase A.
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PMID:Detailed studies on substrate structure requirements of glycoamidases A and F. 934 Nov 45