An improved method of separating glucosaminitol from galactosaminitol and their amino sugars on an amino acid analyzer

Subunit structure of deglycosylated human and swine trachea and Cowper's gland mucin glycoproteins

The oligosaccharide chains in human and swine trachea and Cowper's gland mucin glycoproteins were completely removed in order to examine the subunit structure and properties of the polypeptide chains of these glycoproteins. The carbohydrate, which constitutes more than 70% of these glycoproteins, was removed by two treatments with trifluoromethanesulfonic acid for 3 h at 3 degrees and periodate oxidation by a modified Smith degradation. All of the sialic acid, fucose, galactose, N-acetylglucosamine and N-acetylgalactosamine present in these glycoproteins was removed by these procedures. The deglycosylated polypeptide chains were purified and characterized. The size of the monomeric forms of all three polypeptide chains were very similar. Data obtained by gel filtration, release of amino acids during hydrolysis with carboxypeptidase B and gel electrophoresis in the presence of 0.1% dodecyl sulfate showed that a major fraction from each of the three mucin glycoproteins had a molecular size of about 67 kDa. All of the deglycosylated chains had a tendency to aggregate. Digestion with carboxypeptidases showed that human and swine trachea mucin glycoproteins had identical carboxyl terminal sequences, -Val-Ala-Phe-Tyr-Leu-Lys-Arg-COOH. Cowper's gland mucin glycoprotein had a similar carboxyl terminal sequence, -Val-Ala-Tyr-Leu-Phe-Arg-Arg-COOH. The yield of amino acids after long periods of hydrolysis with carboxypeptidases showed that at least 85% of the polypeptide chains in each of the deglycosylated preparations have these sequences. These results suggested that the polypeptide chains in these deglycosylated mucin glycoprotein preparations were relatively homogeneous. The deglycosylated polypeptide chains as well as the intact mucin glycoproteins had blocked amino terminii. The purified polypeptide chains were digested with trypsin-TCPK, and S. aureus V8 protease and the resulting peptides were isolated by gel electrophoresis in the presence of 0.1% dodecyl sulfate and by HPLC. Two partial amino acid sequences from swine trachea mucin glycoprotein, two partial sequences from human trachea mucin glycoprotein and three partial sequences from Cowper's gland mucin glycoprotein were determined. The partial amino acid sequences of the peptides isolated from swine trachea mucin glycoprotein showed more than 70% sequence homology to a repeating sequence present in porcine submaxillary mucin glycoprotein. Five to eight immunoprecipitable bands with sizes ranging from about 40 kDa to 46 kDa were seen when the polypeptide chains were digested with S. aureus V8 protease. All of the bands had blocked amino terminii and differed by a constant molecular weight of about 1.5 kDa.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

A pathway of polygalactosamine formation in Aspergillus parasiticus: enzymatic deacetylation of N-acetylated polygalactosamine

1. An enzyme which hydrolyzes the acetamido groups of N-acetylgalactosamine residues in N-acetylated polygalactosamine was found in the supernatant fraction of Aspergillus parasiticus AHU 7165, a polygalactosamine-producing strain. 2. N-Acetylated polygalactosamine was used as a substrate in the purification and characterization of this enzyme. A 140-fold purification was obtained by means of ammonium sulfate fractionation followed by chromatography on carboxymethylcellulose and DEAE-cellulose. 3. The enzyme releases about 60-70% of the acetyl groups of N-acetylated polygalactosamine, giving a product with free amino groups. Whereas the enzyme also deacetylates oligosaccharides with 14 or more N-acetylgalactosamine units at a rate similar to that of deacetylation of the polymer, it deacetylates shorter oligosaccharides (trimer to hexamer of N-acetylgalactosamine) much more slowly and is virtually inactive toward disaccharide. Deacetylation can not be detected with bacterial cell wall peptidoglycan, N-acetylated heparin, partially O-hydroxyethylated chitin or monomeric N-acetylgalactosamine derivatives as substrates. 4. This enzyme shows double pH optima of 5.3 and 9.3. The Km value for N-acetylated poly-galactosamine is 0.15 g/l (or 0.54 mM with respect to monosaccharide residues). 5. The occurrence of this enzyme may account for the formation of polygalactosamine with free amino groups.

Isolation and characterization of glycoproteins from canine tracheal mucus

Three homogeneous glycoproteins were isolated from reduced and S-carboxy-methylated canine tracheal pouch mucus by gel filtration and ion-exchange chromatography. Initial fractionation was carried out on Sephadex G-200; chromatography of the excluded Sephadex G-200 fraction on Bio-Gel A-15 m yielded two high molecular weight glycoprotein fractions. Following rechromatography on the same column, the main fraction behaved as an electrophoretically homogeneous high molecular weight (581 600) glycoprotein, with a high carbohydrate content (80%) and a single amino-terminal amino acid (arginine). Ion-exchange chromatography (DEAE-cellulose) of the included Sephadex G-200 fraction yielded two electrophoretically homogeneous glycoproteins of lower molecular weight (20 800 and 24 600, respectively). A single amino-terminal amino acid, glycine and alanine, respectively, was detected for each glycoprotein. Chemical analysis of these three glycoproteins revealed the presence of fucose, galactose, N-acetylgalactosamine, N-acetylglucosamine, N-acetylneuraminic acid and sulfate monoester. The high molecular weight glycoprotein had a higher hexose, sialic acid and sulfate content, per mg of protein, than the low molecular weight glycoproteins. The results of the alkaline borohydride treatment indicated that the majority of the carbohydrate chains of these glycoproteins are linked to the protein core through O-glycosidic bonds involving N-acetylgalactosamine and serine or threonine.

Isolation and characterization of three unusual membrane glycopeptides present in rat intestinal endoplasmic reticula

Three glycopeptides have been isolated from the mucosal homogenates of the rat small intestine without using proteolysis. These glycopeptides appear to be localized exclusively in the membranes of the endoplasmic reticula. Although they have similar molecular weights of about 2550 and have similar amino acid compositions, they differ in the carbohydrate constituents. The major glycopeptide has 2 mol glucose per polypeptide chain while the two other glycopeptides contain 1 mol fucose, mannose and galactose with either 1 or 2 mol glucose. No hexosamine or sialic acid was detected in any of the glycopeptides. An unusual physical property was found associated with these glycopeptides. Below pH 6.5 they formed a precipitate which prevented them from diffusing through a dialysis membrane and allowed them to be rapidly purified following solubilization from the membrane. These glycopeptides appear to represent a new group of heretofore uncharacterized membrane constitutents which may play a role in some function specific for the endoplasmic reticula.

The isolation and characterization of rat sublingual mucus-glycoprotein

A purified glycoprotein, designated RSL-major, was isolated from the rat sublingual gland by means of the procedure of Tettamanti and Pigman. It was found to be homogeneous by analytical ultracentrifugation, to have a mol. wt. of 2-2 times 10-6, and to contain 81 percent (W/W) of carbohydrate, which consists mainly of sialic acid, 2-acetamido-2-deocy-D-glucose, 2-acetamido-2-deocy-D-galactose, and D-galactose in the molar ratio of 1.4:1.4:1.0:1.5; small amounts of fucose and mannose [1.2 and 2.8 percent (W/W), respectively] were also present. The sialic acid residues were resistant to the action of V. cholerae neuraminidase. This resistance was completely abolished by removal of the O-acetyl groups contained in the sialic acid. The sialic acid in RSL-major appeared to be a mixture of N-acetyl-4-O-acetyl- and N-acetyl-4, 7(8)-di-O-acetylneuraminic acids. The carbohydrate to protein attachment of RSL-major was shown, by alkaline beta-elimination reaction, to consist of an O-glycosyl linkage between 2-acetamido-2-deoxy-D-galactosyl residues in the oligosaccharide chains and seryl and threonyl residues in the protein core. The average oligosaccharide, contained in RSL-major, was postulated to be a heptasaccharide. A second material, designated RSL-minor, and also isolated from the ratsublingual gland, was obtained as a mixture of glycoprotein(s) and hydroxylapatite gel, and was not purified further.

Alterations of membrane glycopeptides in human colonic adenocarcinoma

Membrane glycopeptides were examined in human colonic adenocarcinoma and normal colonic mucosa. The carbohydrates of membrane glycopeptides were found to be markedly reduced in tumor tissue and the relative proportions of the various sugars were altered. Although all of the sugars were lower in tumor tissue when compared to the adjacent normal mucosa, galactosamine, fucose, and sialic acid were more significantly reduced. Examination of the blood group activity and lectin-binding properties of membrane glycopeptides revealed that specific carbohydrate structures had changed in the tumor tissue. Most striking of these changes was the disappearance of glycoprotein-associated blood group A activity. Assay of the enzyme responsible for synthesis of the blood group A determinant showed that this glycosyltransferase activity was greatly diminished in tumor tissue. A galactosyltransferase and a fucosyltransferase were also significantly lower in the tumor tissue whereas the levels of another galactosyltransferase and a sialyltransferase were unaltered. Glycosidase activities in the normal and tumor tissues were similar. The results show that an alteration in glycoprotein biosynthesis occurred during tumorigenesis that resulted in a modified membrane glycoprotein composition and that these changes are probably a reflection of reduced levels of the enzymes responsible for glycoprotein synthesis.

Studies of the polysaccharide fraction from the lipopolysaccharide of Pseudomonas alcaligenes

Studies of the lipopolysaccharide of Pseudomonas alcaligenes strain BR 1/2 were extended to the polysaccharide moiety. The crude polysaccharide, obtained by mild acid hydrolysis of the lipopolysaccharide, was fractionated by gel filtration. The major fraction was the phosphorylated polysaccharide, for which the approximate proportions of residues were; glucose (2), rhamnose (0.7), heptose (2-3), galactosamine (1), alanine (1), 3-deoxy-2-octulonic acid (1), phosphorus (5-6). The heptose was l-glycero-d-manno-heptose. The minor fractions from gel filtration contained free 3-deoxy-2-octulonic acid, P(i) and PP(i). The purified polysaccharide was studied by periodate oxidation, methylation analysis, partial hydrolysis, and dephosphorylation. All the rhamnose and part of the glucose and heptose occur as non-reducing terminal residues. Other glucose residues are 3-substituted, and most heptose residues are esterified with condensed phosphate residues, possibly in the C-4 position. Free heptose and a heptosylglucose were isolated from a partial hydrolysate of the polysaccharide. The location of galactosamine in the polysaccharide was not established, but either the C-3 or C-4 position appears to be substituted and a linkage to alanine was indicated. In its composition, the polysaccharide from Ps. alcaligenes resembles core polysaccharides from other pseudomonads: no possible side-chain polysaccharide was detected.

Glycoprotein biosynthesis in small intestine. 3. Enzymatic basis for the difference in the antigenicity of mucins

Rat small intestinal mucosa was examined for ability to produce mucins with human blood group A, B, and H activity. Blood group activity of the mucins was compared to antigenic activity of red blood cells in individual rats and the enzymatic basis for differences was investigated. Red cells in all the rats examined contained human blood group A and B antigens. All rats synthesized intestinal mucins having B and H antigenic activity but 57% failed to produce mucins with blood group A activity (A(-)); the remaining 43% (A(+)) produced A substance. The activities of five glycosyltransferases including alpha(1-->2) fucosyltransferase, the determinant of human secretor status, were measured in the intestine of A(+) and A(-) rats. Four enzymes were the same in both groups, while the fifth, N-acetylgalactosaminyltransferase, was present only in A(+) rats. The specificity of this latter enzyme, as found in the rat, appeared similar to that in humans, since it catalyzed addition of N-acetyl-D-galactosamine only to acceptors which had the H determinant structure. In the presence of the enzyme, A(-) mucin could be converted to A(+) mucin; this was shown both by hemagglutination inhibition and immunoprecipitin studies of the products of incubation of A(-) mucin with UDP-N-acetyl-D-galactosamine and the enzyme. These studies indicate that the difference between A(+) and A(-) rats is due to the apparent absence of N-acetylgalactosaminyltransferase in the intestinal mucosa of A(-) rats. These rats may provide experimental models for studies on the effect of ABO and secretor status on susceptibility to ulceration and carcinogenesis.