Isolation and characterization of an endo-beta-galactosidase from a new strain of Escherichia freundii

Selective release of the disaccharide 2-acetamido-2-deoxy-3-O-(beta-D-galactopyranosyl)-D-galactose from epiglycanin by endo-N-acetyl-alpha-D-galactosaminidase

Epiglycanin, the major glycoprotein of TA3-Ha mammary carcinoma ascites cells, was radiolabeled with tritium in the terminal D-galactose and 2-acetamido-2-deoxy-D-galactose residues. Alkaline-borohydride treatment, reported to release five O-glycosyl-linked chain types from epiglycanin, resulted in the cleavage of 98-99% of the radioactivity from the protein. Of this, 63% of the radioactivity from epiglycanin and 70% from asialoepiglycanin co-migrated with an authentic sample of 2-acetamido-2-deoxy-3-O-(beta-D-galactopyranosyl)-D-galactitol on a column of Bio-Gel P-6. Incubation of [3H]galactose-epiglycanin with endo-N-acetyl -alpha-D-galactosaminidase (Diplococcus pneumoniae), and fractionation of the mixture on a column of Bio-Gel P-4, gave only one oligosaccharide peak containing 62 and 70%, respectively, of the radioactivity of epiglycanin and asialoepiglycanin. This oligosaccharide comigrated with authentic 2-acetamido-2-deoxy-3-O-(beta-D-galactopyranosyl)-D-galactose (1) on columns of Bio-Gel P-2 and P-4 and on paper chromatograms. Results of experiments in which unlabeled epiglycanin was treated with enzyme and the products analyzed, by three different methods, suggested that 78-85% of 1 had been cleaved. Another enzyme, N-acetyl-alpha-D-galactosaminyl-oligosaccharidase from Clostridium perfringens, exhibited similar specificity and cleaved 65% of the radioactivity from ([3H]galactose)asialoepiglycanin, which was eluted from a Bio-Gel P-2 column as the disaccharide 1.

Proteoglycans of rabbit cornea: labelling in organ culture and in vivo

Rabbit corneas maintained with radioactively-labelled precursors in organ culture for up to 42 hr produced labelled proteoglycans of the same kind as those that exist normally or that are produced by labelling in vivo. Whole corneas, including a narrow strip of sclera, were kept in culture in the presence of [3H]-glucosamine and [35S]-sulfate. The rate of incorporation of sulfate into extractable proteoglycans was linear over the time investigated, as was the rate of incorporation of glucosamine after a short lag. Three labelled proteoglycans were isolated and found to behave in ion-exchange chromatography and gel chromatography in the same way as they did in previous studies by chemical analysis. Their labelled glycosaminoglycans were primarily dermatan sulfate and keratan sulfate, with traces of hyaluronic acid and heparan sulfate. When labelled precursors were injected directly into the anterior chamber of rabbit eyes, the resulting labelled proteoglycans were similar to those obtained in organ culture. Both in vivo and during organ culture, the specific activity of hexosamine in the keratan sulfate proteoglycans was about one-half that in dermatan sulfate, probably because of different synthetic rates or different specific activities of immediate precursors.

Partial characterization of sialoglycopeptides produced by cultured human melanoma cells and melanocytes

The sialoglycopeptides produced by HM7 human melanoma and fetal uveal melanocyte cultures grown in the presence of [3H]glucosamine and [35S]sulfate were isolated from the Pronase digests of cells, spent media, and intracellular material. From the melanoma culture, six sialoglycopeptides, accounting for 43% of the total 3H radioactivity in the nondiffusible cell-associated glycopeptides, were purified. A major glycopeptide (GPIb) having an apparent molecular weight in the range 12 000-15 000 showed specific sialic acid dependent to interaction with wheat germ agglutinin (WGA). It was found to contain mainly O-glycosidically linked oligosaccharides having the structure (AcNeu) leads to 0-2[Gal leads to GalNAc]; some N-glycosidically linked saccharides were also present. A second WGA-binding glycopeptide (GPIa) was smaller and less anionic and had a higher proportion of N-glycosidically linked saccharides than GPIb. The normal fetal cultures yielded either no (iris) or markedly reduced (melanocytes) quantities of the WGA-binding glycopeptides. The four WGA-nonbinding sialoglycopeotides purified from melanoma were shown to have complex (N-acetyllactosaminly type) oligosaccharides linked via N-acetylglucosamine to asparagine with either no or insignificant amounts of O-glycosidically linked saccharides. The corresponding glycopeptides from melanocytes were of smaller molecular size and lower anionic charge, reflecting an overall lower degree of glycosylation.

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.