Presence of endo-beta-N-acetylglucosaminidase and protease activities in the commercial neuraminidase preparations isolated from Clostridium perfringens

A clostridial endo-beta-galactosidase that cleaves both blood group A and B glycotopes: the first member of a new glycoside hydrolase family, GH98

We have isolated an endo-beta-galactosidase designated E-ABase from Clostridium perfringens ATCC 10543 capable of liberating both the A trisaccharide (A-Tri; GalNAcalpha1-->3(Fucalpha1-->2)Gal) and B trisaccharide (B-Tri; Galalpha1-->3(Fucalpha1-->2)Gal) from glycoconjugates containing blood group A and B glycotopes, respectively. We have subsequently cloned the gene (eabC) that encodes E-ABase from this organism. This gene was found to be identical to the CPE0329 gene of C. perfringens strain 13, whose product was labeled as a hypothetical protein (Shimizu, T., Ohtani, K., Hirakawa, H., Ohshima, K., Yamashita, A., Shiba, T., Ogasawara, N., Hattori, M., Kuhara, S., and Hayashi, H. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 996-1001). Since the amino acid sequence of E-ABase does not bear detectable similarity to any of the 97 existing families of glycoside hydrolases, we have proposed to assign this unusual enzyme to a new family, GH98. We also expressed eabC in Escherichia coli BL21(DE3) and obtained 27 mg of fully active recombinant E-ABase from 1 liter of culture. Recombinant E-ABase not only destroyed the blood group A and B antigenicity of human type A and B erythrocytes, but also released A-Tri and B-Tri from blood group A(+)- and B(+)- containing glycoconjugates. The structures of A-Tri and B-Tri liberated from A(+) porcine gastric mucin and B(+) human ovarian cyst glycoprotein were established by NMR spectroscopy. The unique specificity of E-ABase should make it useful for studying the structure and function of blood group A- and B-containing glycoconju-gates as well as for identifying other glycosidases belonging to the new GH98 family.

Molecular genetic analysis of the nagH gene encoding a hyaluronidase of Clostridium perfringens

A recombinant lambda phage was identified in a Clostridium perfringens genomic library by means of its ability to hydrolyse the fluorescent substrate 4-methyl-umbelliferyl-beta-D-glucosaminide, isolated and shown to encode an endo-beta-N-acetylglucosaminidase. This enzyme, NagH, is also known as hyaluronidase, or Mu toxin, a putative virulence factor which is likely to act on connective tissue during gas gangrene. Nucleotide sequence analysis allowed the primary structure to be deduced and showed hyaluronidase to be a large exported protein of 114,392 Daltons and an enzyme of this size, endowed with the corresponding activities, was partially purified from C. perfringens. Hyaluronidase seems to be organised into two domains, an N-terminal region comprising 700 amino acids bearing the active site and a 300-residue C-terminal segment, containing three copies of an extended motif. Two other reading frames, linked to nagH, also appear to encode proteins with sugar-binding motifs.

Molecular genetics and pathogenesis of Clostridium perfringens

Clostridium perfringens is the causative agent of a number of human diseases, such as gas gangrene and food poisoning, and many diseases of animals. Recently significant advances have been made in the development of C. perfringens genetics. Studies on bacteriocin plasmids and conjugative R plasmids have led to the cloning and analysis of many C. perfringens genes and the construction of shuttle plasmids. The relationship of antibiotic resistance genes to similar genes from other bacteria has been elucidated. A detailed physical map of the C. perfringens chromosome has been prepared, and numerous genes have been located on that map. Reproducible transformation methods for the introduction of plasmids into C. perfringens have been developed, and several genes coding for the production of extracellular toxins and enzymes have been cloned. Now that it is possible to freely move genetic information back and forth between C. perfringens and Escherichia coli, it will be possible to apply modern molecular methods to studies on the pathogenesis of C. perfringens infections.

Optimizing hydrolysis of N-linked high-mannose oligosaccharides by endo-beta-N-acetylglucosaminidase H

The ability of endo-beta-acetylglucosaminidase H (Endo H) from Streptomyces plicatus to hydrolyze high-mannose oligosaccharides from glycoproteins is influenced by numerous factors, including the tertiary structure of the substrate glycoproteins, the amount of Endo H used, the time of incubation, and the presence or absence of reagents that affect protein configuration. Endo H levels below 10 to 20 milliunits/ml may incompletely hydrolyze oligosaccharides, regardless of the incubation time, because even though the enzyme remains active, it becomes trapped or sequestered and is unavailable. Endo H activity can be potentiated by first denaturing substrate glycoproteins in a 1.2-fold weight excess of sodium dodecyl sulfate prior to hydrolysis. However, low levels of Endo H are sensitive to inactivation by sodium dodecyl sulfate, with considerable activity being lost over 4 h when the unbound detergent concentration exceeds protein by 0.02% (0.2 mg/ml). Other denaturants such as the Tritons, the zwittergents, the Brij series, or octylglucoside do not enhance or inhibit Endo H removal of oligosaccharides, but the chaotropic salt sodium thiocyanate at 0.5 M enhances Endo H action on some glycoproteins, particularly bovine thyroglobulin. Under denaturing conditions, proteolytic contaminants are a potential problem. Addition of 1 mM phenylmethylsulfonyl fluoride to Endo H incubations completely inhibits the residual Endo H-associated protease(s). Furthermore, Endo H is unaffected by a wide range of proteolytic inhibitors that may be used to protect substrate glycoproteins.

Isolation of two endo-beta-N-acetylglucosaminidases from fig latex

Two endo-beta-N-acetylglucosaminidases (mannosyl-glycoprotein 1,4-N-acetamidodeoxy-beta-D-glycohydrolase, EC 3.2.1.96) (type F-I and type F-II) have been isolated from fig latex. At pH 7.0, type F-1 was retained by the DEAE-Sephadex A-50 column, whereas type F-II was not adsorbed by the column. The optimum pH of type F-I was found to be pH 5.9 and type F-II, pH 5.4. Type F-I enzyme hydrolyzes the tri-mannosyl derivatives di-N-acetylglucosaminylasparagine faster than the penta- or hexa-mannosyl compounds. Type F-II hydrolyzes the penta- and hexa-mannosyl derivatives, but not the tri-mannosyl compound.

Mannosyl transfer by membranes of Aspergillus niger: mannosylation of endogenous acceptors and partial analysis of the products

A smooth membrane fraction of Aspergillus niger catalyzed the transfer of mannose from GDP-mannose to endogenous lipid and protein acceptors. The mannolipid was acidic, as judged by diethylaminoethyl-cellulose chromatography, and had a mobility similar to ficaprenyl phosphate on thin-layer chromatograms. Mannose transfer occurred optimally at pH 6.5 to 7.5 and required Mn(2+) for use of the protein as acceptor, but either Mn(2+) or Mg(2+) with the lipid as acceptor. Glycopeptides of the mannosylated protein ([(14)C]gly) and of an alpha-glucosidase (alpha-glu) secreted by the organism were produced by Pronase digestion and separation of the products on Sephadex G-25. Because ovalbumin has a carbohydrate composition similar to that of alpha-glu and because the carbohydrate structure of ovalbumin is known, ovalbumin glycopeptides (Ov) were similarly obtained and used as standards in determining carbohydrate structures. Oligosaccharide chains of [(14)C]gly, alpha-glu, and Ov were obtained by treatment of the respective glycopeptides with endo-beta-N-acetylglucosaminidase, reduction with NaBT(4), and concanavalin A-Sepharose chromatography. The (3)H-labeled oligosaccharides obtained were subjected to the following treatments: (i) digestion with alpha- and beta-mannosidases, (ii) Smith degradation, and (iii) acetolysis. Subsequently, changes in paper chromatographic mobilities were detected. Also, alpha-glu was permethylated, and the partially methylated alditol acetates were analyzed by gas-liquid chromatography. The resultant proposed structure shows that the oligosaccharide chain of alpha-glu is almost identical to that of an Ov chain, while [(14)C]gly has a structure which is probably the same as that of alpha-glu. It is suggested that the transferase(s) involved in [(14)C]gly synthesis in vitro may be responsible for glycosylation of secreted enzymes.

Microheterogeneity of human antithrombin III

Antithrombin purified from normal human plasma has been separated into two fractions by isoelectric focusing in a pH 4-6 gradient. These fractions were homogeneous by polyacrylamide gel electrophoresis, had similar amino acid composition and the same specific activity. Both of them cross reacted with antiserum against antithrombin. They were found to contain different amounts of sialic acid and aminosugars. After neuraminidase treatment only a single, homogeneous peak was found by isoelectric focusing--with unchanged antithrombin activity--suggesting that the microheterogeneity is due to a difference in glycosylation.

Effects of neuraminidase on lectin binding by wild-type and ricin-resistant strains of hamster fibroblasts

The nature of cell surface receptors for ricin on wild-type and ricin-resistant variants of baby hamster kidney fibroblasts has been studied. Neuraminidase stimulated ricin binding threefold by wild-type cells, and increased their susceptibility to ricin toxicity as measured by inhibition of [3H]leucine uptake (LD30 fell from 5.0 to 0.5 microgram/mL). Basal ricin binding by ricin-resistant variants (10-300% that of wild type) was also stimulated (2- to 17-fold) by neuraminidase in all seven clonal strains examined; susceptibility to ricin was greatly increased by neuraminidase in these variants. Neuraminidase did not affect the binding of concanavalin A by wild type or a ricin-resistant variant, but decreased the binding of wheat-germ agglutinin by 90% in both cell types. The trivial binding of peanut agglutinin by wild type and a ricin-resistant variant was markedly enhanced (14- to 22-fold) by neuraminidase. Neither collagenase (50 U/mL) nor Pronase (0.0001%) affected ricin binding by wild type or a ricin-resistant variant. These data suggest the existence of "exposed" and "cryptic" oligosaccharide receptors for ricin on the cell membrane glycoproteins of baby hamster kidney fibroblasts. The cryptic ricin receptors probably include at least the sequence D-galactosyl-beta-(1 replaced by 3)-N-acetylhexosamine substituted by sialic acid residues. Exposed and cryptic ricin receptors appear to be different and under separate genetic control.

Attachment of thioglycosides to proteins: enhancement of liver membrane binding

Thioglycosides of D-galactose, D-glucose, N-acetyl-D-glucosamine, and D-mannose were covalently attached to Aspergillus oryzae alpha-amylase, hen's eggs lysozyme, and bovine serum albumin by amidination, diazo coupling, and amide formation. The binding of the newly formed glycoproteins (neoglycoproteins) to rabbit liver membranes was measured, using asialoorosomucoid as a reference. Attachment of D-galactosides by any of the three methods enhanced binding by several orders of magnitude. Coupling of a comparable number of D-mannosides or N-acetyl-D-glucosaminides had little or no effect. Attachment of D-glucosides also enhanced binding but to a variable extent depending on the method of attachment. Thus, the behavior of neoglycoproteins toward rabbit liver membranes closely paralleled that of serum glycoproteins (Ashwell and Morell, 1974) with respect to sugar specificity.