Analysis of endo-beta-N-acetylglucosaminidase activity by high-pressure liquid chromatography on a silica-based chemically bonded octadecyl column

Transglycosylation Activity of Glycosynthase Mutants of Endo-β-N-Acetylglucosaminidase from Coprinopsis cinerea

Endo-β-N-acetylglucosaminidase (ENGase), which catalyzes hydrolysis of N-linked oligosaccharides, is a useful tool for analyzing oligosaccharide contents of glycoproteins. However, there are only a few known ENGases that can catalyze the hydrolysis of human complex type oligosaccharides, and although commercially available, they are expensive. Here, we report the cloning of two ENGase encoding cDNAs from the basidiomycete fungus Coprinopsis cinerea, Endo-CC1 and Endo-CC2. We successfully expressed recombinant His₆-tagged Endo-CC1 and Endo-CC2 in Escherichia coli and purified them for enzymatic characterization. Both Endo-CC1 and Endo-CC2 showed hydrolytic activity on high-mannose and complex type oligosaccharides. Since Endo-CC1 could be prepared more easily than Endo-CC2 from E. coli cultures, we examined the enzymatic properties of Endo-CC1 in detail. Our results showed that Endo-CC1 acted on both N-linked high-mannose type and sialobiantennary type complex oligosaccharides of glycoproteins RNase B and human transferrin, respectively, but not on the sialotriantennary type complex oligosaccharide of glycoprotein fetuin. Examination of the transglycosylation activity of Endo-CC1 revealed that the wild-type Endo-CC1 could not transfer the sialobiantennary type complex oligosaccharide onto the deglycosylated RNase B. To obtain an Endo-CC1 mutant with desired transglycosylation activity, we performed mutation analysis of the active site residue Asn 180 (N180), known to be important for catalysis, by individually replacing it with the remaining 19 amino acid residues. Transglycosylation analyses of these mutants led us to identify one mutant, namely Endo-CC1^N180H, which exhibited the desired transglycosylation activity. Taken together, we suggest that Endo-CC1 would potentially be a valuable tool for analyzing oligosaccharides on glycoproteins, as large quantities of it could be made available more easily and less expensively than the currently used enzyme, Endo-M.

Induction and Purification of Endo-beta-N-Acetylglucosaminidase from Arthrobacter protophormiae Grown in Ovalbumin

Arthrobacter protophormiae produced a high level of extracellular endo-beta-N-acetylglucosaminidase when cells were grown in a medium containing ovalbumin. The enzyme was induced by the glycopeptide fraction of ovalbumin prepared by pronase digestion. Production of the enzyme was also induced by glycoproteins such as yeast invertase and bovine ribonuclease B but not by monosaccharides such as mannose, N-acetylglucosamine, and galactose. The enzyme was purified to homogeneity as demonstrated by polyacrylamide gel electrophoresis and has an apparent molecular weight of about 80,000. The enzyme showed a broad optimum pH in the range of pH 5.0 to 11.0. The enzyme hydrolyzed all heterogeneous ovalbumin glycopeptides, although the hydrolysis rates for hybrid type glycopeptides were very low. The substrate specificity of A. protophormiae endo-beta-N-acetylglucosaminidase was very similar to that of Endo-C(II) from Clostridium perfringens. Therefore, the enzyme induction by A. protophormiae seems to have a close relation to the substrate specificity of the enzyme.

Plate assay for endo-β-N-acetylglucosaminidase activity using a chromogenic substrate synthesized by transglycosylation with Arthrobacter Endo-β-N-acetylglucosaminidase

The transglycosylation activity of Arthrobacter endo-beta-N-acetylglucosaminidase (Endo-A) was used for the enzymatic synthesis of a novel oligosaccharide, Man6GlcNAc-5-bromo-4-chloro-3-indolyl-beta-glucoside (Man6GlcNAc-Glc-beta-X). Various endo-beta-N-acetylglucosaminidases hydrolyzed this oligosaccharide, producing Man6GlcNAc and Glc-beta-X. The E. coli strains coexpressing Endo-A and beta-glucosidase formed blue colonies in the presence of Man6GlcNAc-Glc-beta-X. Therefore, endo-beta-N-acetylglucosaminidase activity could be directly detected by the plate assay. This simple plate assay is useful for screening microorganisms for endo-beta-N-acetylglucosaminidase activity.

Enzymatic synthesis of a neoglycoconjugate by transglycosylation with Arthrobacter endo-beta-N-acetylglucosaminidase: a substrate for colorimetric detection of endo-beta-N-acetylglucosaminidase activity

The transglycosylation activity of endo-beta-N-acetylglucosaminidase from Arthrobacter protophormiae was used for the enzymatic synthesis of a novel oligosaccharide, Man6GlcNAc-p-nitrophenyl-alpha-D-glucose (Man6GlcNAc-Glc-pNP). The reaction was efficiently induced in aqueous solution containing dimethyl sulfoxide. In the medium containing 20% (v/v) dimethyl sulfoxide with 0.1 M Glc-pNP as an acceptor, the transglycosylation attained yields of 75% by high-performance anion-exchange chromatography. The structure of Man6GlcNAc-Glc-pNP was confirmed by ion mass spectrometry and 400 MHz 1H NMR spectrometry. Various endo-beta-N-acetylglucosaminidases hydrolyzed this oligosaccharide and Man6GlcNAc and Glc-pNP were released from the oligosaccharide by endo-beta-N-acetylglucosaminidase digestion. We have established a new procedure for the colorimetric detection of endo-beta-N-acetylglucosaminidase activity using Man6Glc-NAc-Glc-pNP, which is simple as that for other exoglycosidase assays with pNP-glycosides as substrates.

Quantitation of the glycation intermediate 3-deoxyglucosone by oxidation with rabbit liver oxoaldehyde dehydrogenase to 2-keto-3-deoxygluconic acid followed by high-performance liquid chromatography

A simple and sensitive method for the detection of 3-deoxyglucosone was developed using oxidation with crude oxoaldehyde dehydrogenase to 2-keto-3-deoxygluconic acid followed by high-performance liquid chromatography (HPLC). Oxoaldehyde dehydrogenase was prepared from rabbit liver and partially characterized. 2-Keto-3-deoxygluconic acid produced from 3-deoxyglucosone by oxoaldehyde dehydrogenase was derivatized with 1,2-diamino-4,5-methylenedioxybenzene, and the fluorescent products were detected and quantitated by HPLC using a solvent containing borate. In the presence of borate, 2-keto-3-deoxygluconic acid was completely separated from N-acetylneuraminic acid. The detection limit of 3-deoxyglucosone was 2.5 pmol/injection (10 microliters) at a signal-to-noise ratio of 3. This method was used to confirm the inhibitory effect of aminoguanidine on glycation.

Analysis of aspartylglucosamine at the picomole level by high-performance liquid chromatography

A sensitive method for quantitative analysis of aspartylglucosamine as its dabsyl chloride derivative by high-performance liquid chromatography is described. Precolumn-derivatized aspartylglucosamine and internal standard (carboxymethylcysteine) are separated on a reversed-phase column with a mobile phase consisting of phosphate buffer and acetonitrile and monitored by UV-VIS detection at 436 nm. Aspartylglucosamine acts in the assay like a polar amino acid, and it can be separated from interfering substances in urine with a retention time of ca. 13 min. Its detection limit is ca. 0.3 microM in water and 0.5-1.0 microM in urine and other biological samples, which permits its quantitation in normal urine, for example. The within-day coefficient of variation is less than 4.7% and the day-to-day coefficient of variation is less than 8.3%. The present method is applicable to the direct analysis of aspartylglucosamine in body fluids and tissues without any prepurification and, in combination with automated liquid chromatography, allows rapid assay of a large number of samples in the detection of aspartylglycosaminuria. The sensitivity of the assay also allows direct quantitation of aspartylglucosamine in normal urine and leukocytes of aspartylglycosaminuria patients, and may thus be used in metabolic studies of the compound.

Detection of UDP-N-acetylgalactosamine-oligosaccharide N-acetylgalactosaminyltransferase activity in rat stomach and human serum by high-performance liquid chromatography

The enzymatic transfer of the sugar portion from UDP-N-acetylgalactosamine to pyridylamino (PA) lacto-N-fucopentaose I (Fuc alpha 1-2Gal beta 1-3GlcNAc beta 1-4Glc-PA) was detected by high-performance liquid chromatography. Separation of the fluorescent product from the fluorescence-labeled acceptor was achieved within 10 min by reversed-phase high-performance liquid chromatography. Rat stomach enzyme activity was detected in the microsomal fraction from antrum but not corpus. Ohara et al. (1986, Comp. Biochem. Physiol. 83B, 273-275) reported that the N-acetylgalactosamine content in antrum mucin was greater than that in corpus mucin and antrum mucin had strong blood group A activity. The prominent asymmetrical distribution of the enzyme detected here well supports these findings. The elution position of the fluorescent product was the same as that of the product formed by the action of type A human serum toward the acceptor. Its hydrolysis by alpha-N-acetylgalactosaminidase yielded the acceptor. It is thus evident that the detected enzyme is the same as that producing the blood group A structure.

Comparative study of specific alpha-1,2-glucosidase activity toward glucosyl galactosyl hydroxylysine in various animal species

1. Assay of the activity of alpha-1,2-glucosidase was completed within 10 min using reversed-phase high performance liquid chromatography and purified dansylated glucosyl galactosyl hydroxylysine as the substrate. 2. A comparative study was made on the enzyme activity of liver homogenate from eight animal species, mouse, frog, chicken, rabbit, pig, rat, human, bovine and that of a spinach leaf homogenate. alpha-1,2-glucosidase activity in human and bovine liver was very low, and that of alpha-1,2-glucosidase could not be detected in the spinach homogenate as expected. 3. 1-deoxynojirimycin, a well known potent inhibitor of alpha-1,2-glucosidases which act on the N-glycosidic type carbohydrate chain, also inhibited alpha-1,2-glucosidase acting specificity on glucosyl galactosyl hydroxylysine derived from the collagen molecule.

Endo-N-acetyl-beta-D-glucosaminidase activity in rat liver. Studies on substrate specificity, enzyme inhibition, subcellular localization and partial purification

Endo-N-acetyl-beta-D-glucosaminidase (EC 3.2.1.96, endoglucosaminidase) has been partially purified (520-fold with respect to the cytoplasmic activity) by using concanavalin A-Sepharose, CM-Sephadex and Bio-Gel P-150 chromatography. From the influence of exogenous glycopeptides on the endoglucosaminidase activity it can be concluded that this activity consists of one enzyme hydrolysing both N-acetyl-lactosaminic-type and oligomannosidic-type substrates. Glycoproteins present in the homogenate inhibit the endoglucosaminidase activity. On re-examination of the subcellular distribution of endoglucosaminidase (after removal of inhibiting glycoproteins from the respective subcellular fractions), its cytoplasmic localization was confirmed.

The use of mannan-Sepharose 4B affinity chromatography for the purification of endo-beta-N-acetylglucosaminidase from Bacillus alvei

In order to facilitate the isolation of endo-beta-N-acetylglucosaminidase for the structural analysis of glycoconjugates, we have isolated a strain of Bacillus alvei which produces a high level of endo-beta-N-acetylglucosaminidase. We have also devised a simple procedure for the purification of endo-beta-N-acetylglucosaminidase from B. alvei using mannan-Sepharose affinity chromatography. By using this method, endo-beta-N-acetylglucosaminidase was purified 3300-fold with 85% yield from the crude enzyme obtained by ammonium sulfate precipitation of the culture medium. The molecular weight of this enzyme was estimated to be about 66 000 by gel filtration. When using (Man)6(GlcNAc)2-Asn-Dns as substrate, the optimal activity occurs at pH 6.5 with Km of 1.9 mM. The action of endo-beta-N-acetylglucosaminidase toward several glycopeptides was also studied.