Purification and characterization of an O-GlcNAc selective N-acetyl-beta-D-glucosaminidase from rat spleen cytosol

Glycosylation of nuclear and cytoplasmic proteins by O-linked N-acetylglucosamine (O-GlcNAc) monosaccharides is an abundant, ubiquitous, and transient post-translational modification. To characterize enzymes involved in removal of these sugars, a neutral and cytoplasmic N-acetyl-beta-D-glucosaminidase (O-GlcNAcase) with strong selectivity for O-GlcNAc-synthetic glycopeptides has been purified over 22,000-fold from rat spleen homogenate. The purified O-GlcNAcase has two major polypeptides of apparent M(r) = 54,000 (alpha subunit) and M(r) = 51,000 (beta subunit). Enzyme activity sediments at M(r) = 106,000 on sucrose gradients, indicating that the native O-GlcNAcase is an alpha beta heterodimer. The O-GlcNAcase also shows substantially stronger relative activity against O-GlcNAc-synthetic glycopeptides than other hexosaminidases. Unlike acidic lysosomal hexosaminidases, O-GlcNAcase is not inhibited by GalNAc or its analogs, has no other detectable glycosidase activities, and does not cross-react with antibodies against acidic hexosaminidases. Subcellular fractionation and latency studies demonstrate the cytoplasmic and nucleoplasmic localization of the enzyme and its ubiquitous presence in tissues. These studies suggest that O-GlcNAcase is involved in the regulated removal of O-GlcNAc from O-GlcNAc-bearing glycoproteins in the nucleoplasmic and cytoplasmic compartments of cells.

Purification and characterization of two forms of N-acetylglucosaminidase from Candida albicans showing widely different outer chain glycosylation

Two forms of N-acetylglucosaminidase were purified to homogeneity by ion exchange (TSK DEAE-3SW, Aquapore CX-300) and gel filtration (TSK G4000 SW) HPLC of Candida albicans ATCC 10261 culture filtrates. Synthesis and secretion of N-acetylglucosaminidase were induced by incubating starved yeast cells at 37 degrees C in medium containing N-acetylglucosamine (GlcNAc). The form of the enzyme depended on the cell growth and starvation conditions before GlcNAc induction. N-Acetylglucosaminidase A (32% total carbohydrate, M(r) 85,000 subunit) was isolated from cells grown in glucose/salts/biotin medium, and N-acetylglucosaminidase B (56% carbohydrate, M(r) 132,000 subunit) was isolated from cells grown in yeast extract/peptone/dextrose. The estimated relative molecular masses of the native enzymes, based on Sephacryl S-300 gel filtration were: A form, 350,000; B form, 600,000; A and B forms after endoglycosidase H (endo H) treatment, 180,000. The purified enzymes migrated on SDS polyacrylamide gels as heterogeneous glycoproteins of M(r) centred at approximately 100,000 (A) and approximately 150,000 (B) but were reduced to a single 58,000 band after denaturation with SDS and cleavage of asparagine-linked sidechains by endo H. When the native glycoproteins were treated with endo H, both enzyme forms had three oligosaccharide sidechains of M(r) approximately 3000 that were endo H resistant. Therefore the difference in the size of N-acetylglucosaminidase A and B was due to variations in outer chain glycosylation of endo H-sensitive inner core structures. N-Acetylglucosaminidase was active and stable over a broad pH range with maximum activity against both p-nitrophenylGlcNAc (pNPGlcNAc) and pNPGalNAc at pH 4.0. The kinetic parameters kcat (s-1) and Km (mM) of N-acetylglucosaminidase A using the following substrates were, respectively: pNPGlcNAc, 740, 0.77; pNPGalNAc, 910, 1.26; N,N'-diacetylchitobiose 620, 0.20; and N,N',N"-triacetylchitotriose, 170, 0.044. The enzyme showed substrate inhibition with all substrates above 0.5 mM except for pNPGalNAc.

Molecular cloning and expression of the Candida albicans beta-N-acetylglucosaminidase (HEX1) gene

beta-N-Acetylglucosaminidase was purified from the spent culture medium of Candida albicans A72 grown in the presence of N-acetylglucosamine (GlcNAc). The N-terminal amino acid sequence of the protein was determined, two degenerate oligonucleotide probes were constructed, and a 3.9-kb BamHI fragment of DNA that hybridized to both probes was subcloned from a lambda EMBL4 library of C. albicans A72 genomic DNA. This fragment of DNA contained the entire beta-N-acetylglucosaminidase (HEX1) gene, which consisted of an open reading frame coding for a polypeptide precursor of 562 amino acids with a putative 22-amino-acid leader sequence. The deduced HEX1 amino acid sequence showed similarity to hexosaminidases from a variety of organisms. Growth of C. albicans on GlcNAc induced transcription of HEX1, resulting in increased specific beta-N-acetylglucosaminidase activity. HEX1 mRNA (2.35 kb) from GlcNAc-grown cells was approximately 200 bp larger than HEX1 mRNA from cells grown on glucose. This size difference was suggested to result from the use of alternative transcription termination sites. The cloned HEX1 gene introduced into C. albicans SGY-243 on a plasmid also responded to GlcNAc induction.

Purification and properties of N-acetylglucosaminidase from eggs of the ascidian, Halocynthia roretzi

In several ascidians, beta-D-N-acetylglucosaminidase (GlcNAcase) released from eggs following fertilization is proposed to play a key role in polyspermy block through its binding to the sperm receptor on the vitelline coat [C. C. Lambert (1989) Development 105, 415-420]. In the ascidian Halocynthia roretzi, GlcNAc-specific lectins inhibited the fertilization most strongly among various lectins. Furthermore, GlcNAcase activity was released from the eggs in response to the egg activation. The GlcNAcase was purified from the eggs to apparent homogeneity by chromatographies on DEAE-Toyopearl, SP-Toyopearl, Toyopearl HW-65, and Mono S. The purified enzyme gave a single band on isoelectric focusing with an isoelectric point of 7.0. It gave two bands on SDS/PAGE: the molecular masses of the bands were estimated to be 65 kDa/66 kDa, and 84 kDa/85 kDa under reducing/non-reducing conditions, respectively. The two bands were found to converge to a single band of 56 kDa after deglycosylation, which suggests microheterogeneity in the sugar moiety. The enzyme showed an oligomeric structure with an apparent molecular mass of 520 kDa, estimated by gel filtration. The optimum pH of the activity was around 4.5. The enzyme hydrolyzed both 4-methylumbelliferyl-GlcNAc and 4-methylumbelliferyl-GalNAc, suggesting that it should be characterized as a beta-D-N-acetylhexosaminidase, with Km values of 1.2 mM and 0.52 mM, respectively. The purified enzyme was found to be capable of binding to the vitelline coat in a GlcNAc-specific manner. Immunoblot analysis using antibody raised against the purified GlcNAcase revealed that the enzyme itself is released from the eggs upon fertilization. Thus, the GlcNAcase purified in this study is released from eggs following fertilization and bound to the vitelline coat in order to function in the polyspermy blocking mechanism.

The lysosomal N-acetyl-beta-D-glucosaminidase (NAG) isoenzymes in plasma: study of distribution in a general population by a simple routine chromatofocusing procedure

We have adapted for routine analysis a pre-existing method for separating the three major N-acetyl-beta-D-glucosaminidase (NAG) isoenzyme forms--A, B+I1 and I2--by chromatofocusing followed by fluorimetric assay of the enzyme activity. This method combines good resolution, accurate quantification of the different isoenzymes and high reproducibility with an acceptable degree of analytical precision. We have applied it to studying the isoenzyme levels in the plasma of a general population of 417 subjects and have analysed these enzyme activities as functions of age, sex, body mass and declared alcohol consumption. Unlike the levels of unfractionated enzyme, levels of all the isoenzymes were higher in men than in women at all ages except in the 20-29 year group. Isoenzyme I2 showed the greatest sex difference. On the whole, with increasing age, both sexes showed more or less regular increases in plasma levels of all the isoenzymes. We also found significant correlations for the population as a whole with age and with body mass index. The only significant correlation with alcohol consumption was for B+I1 in men.

[Study on the enzymatic properties of N-acetyl-beta, D-glucosaminidase A (NAG A) from the tissue of renal cell carcinomas: comparison of the enzymatic properties with those of normal renal tissues, with special regard to sugar-chain structures]

The enzymatic properties of N-acetyl-beta,D-glucosaminidase A (NAG A) partially purified from the tissues of seven cases of human renal cell carcinomas were studied individually and compared with those of normal renal tissues. In the carcinoma tissues, the Km value of the enzyme toward a synthetic glucosaminide substrate was 0.180 +/- 0.07 mM, the optimal pH of the enzyme ranged from pH 4.7 to 4.9 and the enzyme showed fairly stable for metal ions. These enzyme characteristics were similar to those of the normal tissues. On the contrary, the sugar-chain structures of the enzyme from the carcinoma tissues studied by lectin affinity chromatographies, were statistically different from those of the normal tissues. Namely, both complex type of sugar-chains as well as hybrid type sugar-chains without fucose linkage to the innermost N-acetylglucosamine (GlcNAc) were significantly increased in the enzyme from the carcinoma tissues, while high mannose type sugar-chains and hybrid type sugar-chains with fucose linkage to the innermost GlcNAc were significantly decreased in the carcinoma tissues compared to the normal tissues. These results indicate that the processing of sugar-chains of the enzyme has possibly changed in the carcinoma tissues.

[Purification and properties of NAG A from human kidney]

In the present paper, we have reported the purification procedures of N-acetyl-beta, D-glucosaminidase (NAG) A from human renal tissue as well as the enzymatic properties of NAG A. NAG A was purified to homogeneity by gel filtration methods using Sephacry S-400 and S-200, followed by affinity chromatography with TSK DEAE 5-PW. The final activity of the enzyme was 1001 U/ml protein which was 506.6-fold that of the crude extract (supernatant of 20,000 x G of the homogenate). The molecular weight of NAG A was 140 kDa, consisting of two subunits of 30 kDa and 57 kDa. The isoelectric point of the enzyme was 5.60. The optimal pH of the enzyme was between 4.7 and 4.9. The Km value of the enzyme for sodio-m-cresol sulfophtaleinyl-N-acetyl-beta, D-glucosaminide was found 0.177 x 10(-3) mol/l. Lectin affinity chromatographies using concanavalin A and wheat germagglutinin have demonstrated that major sugar-chains of the enzyme were the high mannose type and hybrid type with a fucose residue, and that a small amount of the complex type was contained.

Thermostable, salt tolerant, wide pH range novel chitobiase from Vibrio parahemolyticus: isolation, characterization, molecular cloning, and expression

A chitobiase gene from Vibrio parahemolyticus was cloned into plasmid pUC18 in Escherichia coli strain DH5 alpha. The plasmid construct, pC120, contained a 6.4 kb Vibrio DNA insert. The recombinant gene expressed chitobiase [EC 3.2.1.30] activity similar to that found in the native Vibrio. The enzyme was purified by ion exchange, hydroxylapatite and gel permeation chromatographies, and exhibited an apparent molecular weight of 80 kDa on SDS-polyacrylamide gel electrophoresis. Chitobiose and 6 more substrates, including beta-N-acetyl galactosamine glycosides, were hydrolyzed by the recombinant chitobiase, indicating its putative classification as an hexosaminidase [EC 3.2.1.52]. The enzyme was resistant to denaturation by 2 M NaCl, thermostable at 45 degrees C and active over a very unusual (for glycosyl hydrolases) pH range, from 4 to 10. The purified cloned chitobiase gave 4 closely focussed bands on an isoelectric focusing gel, at pH 4 to 6.5. The N-terminal 43 amino acid sequence shows no homology with other proteins in commercial databanks or in the literature, and from its N-terminal sequence, appears to be a novel protein, unrelated in sequence to chitobiases from other Vibrios reported and unrelated to hexosaminidases from other organisms.

Purification and partial characterization of alpha-N-acetylglucosaminidase from human liver

A deficiency in alpha-N-acetylglucosaminidase is known as mucopolysaccharidosis IIIB or Sanfilippo B syndrome. We purified this enzyme almost 39,000-fold from liver to homogeneity with 3% recovery. Use of concanavalin A (Con A)-Sepharose and heparin-Sepharose resulted in 13.4-fold and 11.6-fold purifications of the enzymatic activity, respectively. The molecular mass was estimated to be 300 kDa by gel filtration and 80 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The isoelectric point was 5.1, optimal pH was 4.5, and the Km for p-nitrophenyl alpha-N-acetylglucosamine was 0.13-0.20 mM. The purified enzyme was stable at 50 degrees C for 1 h and within the pH range of 6.5-8.5. Anti-serum against the purified enzyme raised in BALB/c mice inhibited the activities of alpha-N-acetylglucosaminidase.

Bovine N-acetyl-beta-D-glucosaminidase: affinity purification and characterization of its active site with nitrogen containing analogs of N-acetylglucosamine

Two N-acetylglucosaminidases were isolated from bovine kidney with a three step procedure featuring affinity purification on 2-acetamido-1,2,5-trideoxy-1,5-iminoglucitol (2-acetamido-1,2-dideoxynojirimycin, II). The major isoenzyme, Hex A, is an alpha, beta hetero-dimer (57 and 52 kDa) with isoelectric points from pH 5.3 to 6.6 and comprised about 80% of the total activity. Its kinetic properties with respect to discrimination between N-acetylglucosaminide, N-acetylgalactosaminide and the corresponding 6-sulfate ester were similar to human hexosaminidase A. The minor isoenzyme, Hex B, a homodimer, isoelectric points 7.0 to 7.4, was similar to Hex A but was without detectable activity with methylumbelliferyl-N-acetyl-beta-glucosaminide-6-sulfate. Inhibition studies with Hex A were carried out with 2-acetamido-2,5-dideoxy-1,5-imino-D-glucopyranose (2-acetamido-2-deoxynojirimycin, (1), the corresponding 1,5-lactam (III), with II and its N,N-dimethyl derivative, and with 2-acetamido-2-deoxy-D-glucono-1,5-lactone (IV). In comparison with N-acetylglucosamine (Ki 1.9 mM) Hex A was inhibited 10(6)-fold better by I, 2600-fold better by II, 2900-fold better by III, and 55,000-fold better by IV. A slow approach to the inhibition equilibrium was observed with I and IV. For IV and Hex A it is the first example of a slow inhibition of a glycoside hydrolase by the corresponding glycono-1,5-lactone. The pH-dependence of Ki for the permanently cationic N,N-dimethyl II (15.4 microM (pH 3.5) to 0.47 microM (pH 7.0)) indicated that formation of the enzyme inhibitor complex is governed by deprotonation of a group with pKa 5.0. The results are discussed with respect to structural features and water accessibility of the active site.

N-acetyl-beta-D-glucosaminidase (NAG) isoenzymes release from human monocyte-derived macrophages in response to zymosan and human recombinant interferon-gamma

Secretion of N-acetyl-beta-D-glucosaminidase (NAG) isoenzymes by human blood monocyte-derived macrophages in response to zymosan and human recombinant interferon-gamma was studied. Macrophages were found to release NAG in response to zymosan, but interferon-gamma has no effect on secretion. Isoenzyme separation by isoelectric focusing demonstrates that non stimulated and zymosan or interferon-gamma treated macrophages release predominantly NAG B and, to a lesser extent, NAG A isoenzymes. In all these conditions, the intracellular intermediate form NAG I could not be detected in the media. Thus, activated macrophages may not be the source of NAG intermediate forms I and P in pathological or maternal serum. In contrast, macrophages could contribute to a significant elevation of urinary activity and NAG B excretion in response to inflammatory conditions.

Purification and properties of neutral beta-N-acetylglucosaminidase from carp blood

A neutral beta-N-acetylglucosaminidase has been purified to homogeneity from carp blood by a seven-step procedure. It was localized in the cytosol of red blood cells. The purified enzyme was specific to beta-N-acetylglucosaminide and inactive to beta-N-acetylgalactosaminide. It was competitively inhibited by free N-acetylglucosamine, but not by free N-acetylgalactosamine. The optimum pH of the enzyme was 6.5, with a stable pH range of 7.0 to 11.0. The enzyme showed greater heat-lability and anodal electrophoretic mobility than acidic beta-N-acetylglucosaminidases. The Mr value, estimated by sucrose density gradient centrifugation, was 122,000, and the enzyme dissociated into two nonidentical subunits with Mr values of 66,000 and 53,000, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. With respect to the major characteristics, the neutral enzyme in carp blood was supposed to be a counterpart of hexosaminidase C in human and other mammalian tissues.

Purification and characterization of a novel fungal endo-beta-N-acetylglucosaminidase acting on complex oligosaccharides of glycoproteins

A novel endo-beta-N-acetylglucosaminidase acting on complex type sugar chains of glycoproteins was found in the culture broth of a fungus isolated from soil and identified as Mucor hiemalis f. hiemalis on the basis of various characteristics. The endo-beta-N-acetylglucosaminidase, named Endo-M, was purified to almost homogeneity by polyacrylamide gel electrophoresis involving ammonium sulfate fractionation, and column chromatographies on DEAE-Sepharose CL-6B, Sephadex G-200, hydroxylapatite, TSK-gel HW-65F and Con A-Sepharose 4B. The molecular weight of the enzyme was estimated to be about 95,000 by gel chromatography. The optimum pH was found to be 6.0-6.5 and the enzyme was stable in the pH range of 7 to 8. The enzyme showed high activity on dansyl ovalbumin glycopeptide, and also could act on dansyl transferrin glycopeptide, and dansyl asialotransferrin glycopeptide containing biantennary complex type sugar chains. The Km value for dansyl asialotransferrin glycopeptide as the substrate was 2.0 x 10(-3) M. The enzyme released complex type sugar chains from intact asialotransferrin without the addition of any detergent and the liberated sugar chains were identified by chromatography on a Bio-Gel P-4 column, calibrated with markers of known structure, and 1H-NMR analysis.

[Separation and properties of N-acetyl-beta-D-glucosaminidase from human seminal plasma]

N-acetyl-beta-D-glucosaminidase from human seminal plasma has been separated by the cellulose acetate electrophoresis into two components, isoenzyme I and II. The two isoenzymes are readily separated on a DEAE-Sephadex column. Isoenzyme I which has adsorbed to the column, is eluted at 0.1 M NaCl, whereas isoenzyme II has passed through the column. The following enzyme properties have been obtained: 1) Both isoenzymes show the same Km values (0.27 X 10(-3) M) towards sodio-m-cresol-sufonphtaleinyl-N-acetyl-beta-D-glucosaminide . 2) Both isoenzymes show the same pH optima of 5.4. 3) Optimal temperature for isoenzyme I is 50 degrees C, while that for isoenzyme II is 65 degrees C. Isoenzyme II is heat stable, while isoenzyme I is easily denatured by heat. These characteristics of isoenzyme I and II coincide with previous reports of NAG A and B from the spleen and the kidney, respectively. The activity ratio of isoenzyme I and II has been studied for the reproductive tissues. The % ratio of isoenzyme I and II in the epididymal head is 62 and 38, that in the epididymal tail is 42 and 58, and 38:62 in the seminal vesicle, 35:65 in the prostatic gland and 27:73 in the seminal plasma.

Purification of a 51 kDa endo-beta-N-acetylglucosaminidase from Staphylococcus aureus

A bacteriolytic enzyme obtained from the culture fluid of Staphylococcus aureus FDA 209P was purified to homogeneity utilizing dye-ligand affinity column chromatography, hydrophobic interaction high pressure liquid chromatography (HPLC) and hydroxyapatite HPLC. Subsequent characterizations indicated that the purified enzyme acted as endo-beta-N-acetylglucosaminidase. The molecular weight determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was 51,000 and the isoelectric point was higher than 10. The optimum pH for the enzyme activity on whole cells of Micrococcus luteus as a substrate was 8.0. Some heavy metal cations (Cu2+ and Zn2+) inhibited the enzyme activity at a concentration of 0.1 mM and others (Ba2+, Mg2+ and Co2+) showed a stimulating effect at a concentration of 1 mM.

Human ovarian carcinoma beta-N-acetylglucosaminidase isoenzymes and their role in extracellular matrix degradation

Degradation and invasion of basement membrane by tumor cells involves the cooperative hydrolysis of proteoglycans, collagens, and glycoproteins mediated by a number of enzymes including proteases, collagenases, and glycosidases. In order to study these processes in vitro, a tissue culture system was developed in which bovine corneal endothelial cell extracellular matrix (ECM) serves as a substrate for attachment and degradation by human ovarian carcinoma cells. Using this system, a correlation was observed between solubilization of glycoconjugates present in ECM and extracellular levels of beta-N-acetylglucosaminidase (EC 3.2.1.30). To determine the role of individual isoenzymes of beta-N-acetylglucosaminidase (beta-NAG) in ECM degradation, the cellular and secreted forms of the enzyme were fractionated and characterized. Three intracellular isoenzyme forms A, I, and B, were isolated from invasive human ovarian carcinoma cell line A-121. In cell homogenate, forms A and B corresponded to 65 and 33% of total beta-NAG activity, respectively. Form I was found to be localized in the plasma membrane fraction of these cells. Two secreted forms of beta-NAG (As and Bs) were detected in serum-free medium. The separated intracellular and secreted isoenzymes demonstrated similar Km values, ranging from 1 to 5 mM, with p-nitro-B-N-acetylglucosaminide substrate. Treatment of [3H]glucosamine-labeled ECM with the separated isoenzymes of beta-NAG resulted in time- and concentration-dependent releases of radioactivity with potency of 1 greater than B much greater than A. These results suggest that human ovarian carcinoma cell beta-N-acetylglucosaminidase isoenzymes (forms B and A) contribute to ECM degradation as secreted enzymes and form I as a membrane enzyme.

N,N'-diacetylchitobiase of Vibrio harveyi. Primary structure, processing, and evolutionary relationships

The nucleotide sequence of the gene, chb, encoding the outer membrane protein, N,N'-diacetylchitobiase (chitobiase), of the marine bacterium, Vibrio harveyi, has been determined. The amino acid sequence of prechitobiase was derived from the nucleotide sequence. Prechitobiase has a molecular mass of 97,771 Da and consists of 883 amino acid residues. A characteristic signal peptide is present at the amino terminus whose removal is inhibited by the antibiotic, globomycin, suggesting that mature chitobiase is a lipoprotein with a maturation pathway similar to that of the Escherichia coli major outer membrane lipoprotein. A perfect homology to six amino acids at the processing and modification region of the outer membrane lipoprotein of E. coli was found with amino acids 15-19 of the deduced prechitobiase protein sequence. Chitobiase shares similarities and possibly common ancestry with the alpha-chain of the human beta-hexosaminidase. A comparison of the amino acid sequences of chitobiase and the alpha-chain of beta-hexosaminidase gave a highly significant alignment score of 19.1 standard deviation units above a mean randomized alignment score. Primer extension analysis of the promoter region revealed three transcription initiation sites used by E. coli cells harboring the chb gene, two of which were also evident in V. harveyi cells.

Rat liver chitobiase: purification, properties, and role in the lysosomal degradation of Asn-linked glycoproteins

Chitobiase, the lysosomal glycosidase responsible for splitting the GlcNAc beta-D-(1-4)GlcNAc moiety in Asn-linked glycoproteins, was purified over 600-fold from frozen rat livers utilizing an assay with di-N-acetylchitobiose as the substrate. The final preparation showed a major polypeptide of Mr 43,000 (sodium dodecylsulfate-polyacrylamide gel electrophoresis) that was determined to be the chitobiase by an immunological method. The purified chitobiase also hydrolyzed tri- and tetrasaccharides of chitin, which like di-N-acetylchitobiose were not substrates if first reduced by NaBH4. The initial products formed during hydrolysis of the tetrasaccharide were trisaccharide and GlcNAc. These results imply that chitobiase is a "reducing-end exohexosaminidase" which cleaves single GlcNAc units only from the reducing end of oligosaccharides. Fucose, typically found linked to the reducing-end GlcNAc in complex oligosaccharide chains, was found to block this reaction. Additional substrates that were hydrolyzed included GlcNAc beta-D-(1-4)MurNAc, the repeating structure from bacterial cell wall peptidoglycan, and the Man beta-D-(1-4)GlcNAc reducing-end component of glycoproteins. Km and Vm for hydrolysis of these substrates were of similar magnitude as for di-N-acetylchitobiose (6.3 mM and 15 mumol/min/mg protein, respectively). Liver tissues from nin mammalian species were surveyed for the presence of chitobiase activity. The activity was found in rat, mouse, rabbit, and guinea pig liver (Stirling [(1974) FEBS Lett. 39, 171-175] previously observed the enzyme in human liver), but not in dog, sheep, pig, cat, and cow liver. The presence or absence of chitobiase so far observed was found to exactly correlate with the type of oligosaccharide fragments found to accumulate in animals containing genetic or inhibitor-induced lysosomal storage pathologies. The presence of the chitobiase corresponds to the occurrence of one GlcNAc unit at the reducing end of stored oligosaccharides, while the absence of this glycosidase yields fragments with an intact GlcNAc beta-D-(1-4)GlcNAc moiety. These results verify our previous proposal that lysosomal disassembly of glycoproteins to free amino acids and sugars is an ordered, bidirectional pathway in which chitobiase (when present) catalyzes the last step during digestion of the protein-oligosaccharide linkage region.

Purification of endo-N-acetyl-beta-D-glucosaminidase H by substrate-affinity chromatography

Endo-N-acetyl-beta-D-glucosaminidase H (Endo H) was purified to homogeneity (3000-fold) from a culture filtrate to Streptomyces plicatus. The key step was substrate-affinity chromatography, which afforded a 1000-fold purification and yielded a protease- and exoglycosidase-free preparation of Endo H. Proteins from the crude sample were applied to the substrate-affinity column, consisting of yeast-invertase glycopeptides bound to Sepharose-immobilized concanavalin A. After washing off the unbound proteins, Endo H was quantitatively eluted by methyl alpha-D-mannopyranoside. Various conditions were tested to achieve an optimal binding of Endo H to this substrate-affinity gel. After substrate-affinity chromatography, Endo H was separated from the coeluted gylcopeptide substrate and some protein impurities by gel filtration and hydrophobic chromatography.

Presence of two endo-beta-N-acetylglucosaminidases in human kidney

We have isolated for the first time two kinds of endo-beta-N-acetylglucosaminidases (E-beta-GNases) simultaneously from human kidney. E-beta-GNase 1 was purified by water extraction, ammonium sulfate fractionation, and chromatography on Sephadex-G-200, DEAE-Sephadex, concanavalin A-Sepharose and Hypatite C columns. After the DEAE-Sephadex step, 107 units of E-beta-GNase 1 with a specific activity of 0.53 units/mg was obtained and after hydroxyapatite column, the enzyme recovery was 26 units with a specific activity of 10.4 units/mg. This enzyme hydrolyzed the high mannose-type asparaginylglycopeptide efficiently and had little activity toward the complex-type glycopeptide. This enzyme had an pH optimum at about 4.5 and was not inhibited by acetate ion. The Asn residue in a glycopeptide appeared not to be an important recognition site for E-beta-GNase 1 to express its activity because the acetylation or the dansylation of Asn residues as well as the elimination of Asn residue from the glycopeptide did not change the susceptibility of the oligosaccharide to E-beta-GNase 1. E-beta-GNase 2 was purified by water extraction, ammonium sulfate fractionation, and chromatography on Sephadex G-200, DEAE-Sephadex, concanavalin A-Sepharose, and Mono S columns. This enzyme was purified about 110-fold with 6.6% recovery. E-beta-GNase 2 was found to be a novel type of E-beta-GNase that hydrolyzed both the high mannose-type and the complex-type oligosaccharide with chitobiosyl group at the reducing end and without the Asn. E-beta-GNase 2 activity was found to be dependent on a L-aspartamido-beta-D-N-acetylglucosamine amidohydrolase (Asn-GNase) for the hydrolysis of asparaginylglycopeptide. Asn-GNase cleaved off the Asn residue from the glycopeptide, and the resulting oligosaccharide was hydrolyzed by E-beta-GNase 2. Because the acetylation or the dansylation of Asn residue in a glycopeptide rendered the glycopeptide resistant to Asn-GNase, the use of the modified asparaginylglycopeptide could not reveal the existence of E-beta-GNase 2 activity. The pH optimum of E-beta-GNase was found to be about 3.5. Like beta-hexosaminidases, this enzyme was inhibited by acetate ion, suggesting the recognition of GlcNAc moiety by this enzyme.

The lysosomal beta-D-N-acetylglucosaminidase isozymes in human plasma during pregnancy: separation and quantification by a simple automated procedure

beta-D-N-Acetylglucosaminidase isozymes were separated and assayed in the plasma of control healthy individuals and pregnant women by an automated method consisting in chromatofocusing on polybuffer exchanger PBE-94 column, flow-through fluorimetric determination of activity and computer assisted quantification. Under the established optimal conditions the method fractionated beta-D-N-acetylglucosaminidase into four isozymes. A, I2, I1 and B, with the analytical coefficients of variation of 1.8, 2.2, 6.4 and 4.1%, respectively. Duration of a single analysis was 25 min including washing, and 10-15 successive runs could be performed on the same column with good reproducibility. A linear activity response was observed from 1-5 microliters of plasma (depending on the individual isozyme) to 50 microliters, and the detection limit was 0.016 mUnits. Isozyme A was heat labile. Upon sialidase treatment, isozymes A, I2 and I1 released sialic acid and were eluted from the column at less acidic pHs. In healthy individuals isozymes A, I2, I1 and B covered about 62.8, 6.9, 15.0 and 15.1% of the total beta-D-N-acetyl-glucosaminidase activity, respectively. During pregnancy the plasma concentration of all isozymes increased. Isozyme I2 showed the highest enhancement (30-fold), followed by I1 (8-fold), B (5.6-fold) and A (3-fold). Interruption of pregnancy by either physiological delivery or ambulatory abortion was followed by a sharp fall of the concentration of all isozymes reaching, in a few days, the control levels.

Purification and characterization of the autolytic glycosidase of Streptococcus pneumoniae

A new lytic enzyme isolated from Streptococcus pneumoniae has been purified to electrophoretical homogeneity. The enzyme, showing a Mr of 64000, has been characterized as an endo-beta-1,4-N-acetylglucosaminidase that requires choline in the teichoic acid of the cell wall substrate for catalytic activity. In vivo experiments demonstrate that the glucosaminidase behaves as an autolytic enzyme.

Specificity towards oligomannoside and hybrid type glycans of the endo-beta-N-acetylglucosaminidase B from the basidiomycete Sporotrichum dimorphosporum

We have previously shown that an endo-beta-N-acetylglucosaminidase (EC 3.2.1.96) named "Endo B", isolated from culture filtrates of the basidiomycete Sporotrichum dimorphosporum cleaves asialo-, and to some extent, monosialylated bi-antennary glycans of the N-acetyllactosamine type linked to the asparagine residue of peptide or protein moieties [Bouquelet S, Strecker G, Montreuil J, Spik G (1980) Biochimie 62:43-49]. In the present paper, the substrate specificity of the enzyme towards oligomannoside and hybrid type glycans has been analyzed. The results obtained indicate that ovalbumin glycopeptides containing four to seven mannose residues and bovine lactotransferrin glycopeptides containing four to nine mannose residues were completely hydrolyzed by the enzyme. The degree of cleavage was variable among hybrid type structures, since glycopeptides containing the following glycans: (Gal)1(GlcNAc)3(Man)5(GlcNAc)2; (GlcNAc)3(Man)5(GlcNAc)2;(GlcNAc)3(Man)4(GlcNAc)2 were not hydrolyzed by the enzyme while the percentage of hydrolysis of a glycopeptide containing (GlcNAc)2(Man)5(GlcNAc)2 glycan reached 90%. The bovine lactotransferrin was partially deglycosylated (40%) in the absence of non-ionic detergent while native ovalbumin glycoprotein was not hydrolyzed by the enzyme. The oligomannoside- and the N-acetyllactosamine-type degrading activities present in the culture filtrates were not separated at any step of the purification procedure. Both activities were eluted as a single component with an apparent molecular mass of 89 kDa suggesting that they are located on the same enzyme molecule. Endo B represents a powerful tool for removing oligomannoside- and N-acetyllactosamine-type glycans from N-glycopeptides and N-glycoproteins. Moreover, advantages in the use of Endo B in a soluble form as well as in an immobilized form result in its high activity and in its stability to heat denaturation and storage.

Isolation and characterization of chicken liver lysosomes

The distribution patterns of chicken liver lysosomal enzymes were studied in iso-osmotic gradients of Percoll. The lysosomal enzymes separated by Percoll gradients showed three different types of distribution. In contrast with rat liver lysosomes, purified chicken liver lysosomes were very stable during storage at 4 degrees C.