Asialo-alpha 1-acid Glycoprotein Research Articles

Novikoff ascites tumor cells contain N-acetyllactosaminide beta 1 leads to 3 and beta 1 leads to 6 N-acetylglucosaminyltransferase activity.

Novikoff ascites tumor cell homogenate was found to catalyze the transfer of [14C]N-acetylglucosamine from UDP-[14C]GlcNAc to asialo-alpha 1-acid glycoprotein. Mucins appeared to be poor acceptors. Methylation and hydrolysis of the product formed in an incubation with UDP-GlcNAc and asialo-alpha 1-acid [3H]glycoprotein yielded 2,4,6-trimethyl [3H]galactose and 2,3,4-trimethyl [3H]galactose, indicating that N-acetylglucosaminyl residues were introduced to position C-3 and C-6 of the terminal galactoses on the glycoprotein. It is concluded that Novikoff cells contain two N-acetylglucosaminyltransferases which might be involved in the synthesis of linear and branched forms of cell surface polylactosaminoglycans and blood group I/i antigenic structures.

Effect of neuraminidase treatment of IgG and alpha 1-acid glycoprotein on their intestinal transport in suckling rats in vivo.

Binding and transport of rat immunoglobulin G (IgG), human alpha 1-acid glycoprotein, and their neuraminidase-treated derivatives were studied in vivo in the intestine of suckling rats. IgG and asialo-IgG binding was saturable, preceding active transport; the amounts of gut-associated alpha 1-acid glycoprotein and asialo-alpha 1-acid glycoprotein ("binding") were not saturable; and transport was passive. Binding of asialo-IgG to the intestine was significantly higher than that of native IgG, whereas transport rates were similar. No difference was found for both binding and transport of native and asialo-alpha 1-acid glycoprotein. These results suggest an interaction between the heteroglycan moiety of IgG and its intestinal receptor and exclude a role of sialic acid in the intestinal transport of a heterologous, passively absorbed glycoprotein.

The role of sialic acid in the functional activity and the hepatic clearance of C1-INH.

The immunochemical properties, catabolic clearance, and organ distribution of highly purified radiolabeled human C1-INH were studied after treatment with glycosidases. The antigenicity and C1s inhibitory activity of C1-INH were unimpaired after removal of sialic acid residues (60%) or sialic acid and galactose residues (60 and 20%, respectively) with immobilized neuraminidase and beta-galactosidase. Treatment of C1-INH with neuraminidase was associated with increased cathodal migration of the glycoprotein. In vivo studies in the rabbit, however, showed that removal of sialic acid residues resulted in rapid blood clearance of C1-INH and enhanced localization of the asialo C1-INH in the liver. Subsequent removal of penultimate galactose residues returned the survival time in the circulation and organ distribution to near normal. Additionally, simultaneous infusion of asialo-C1-INH with asialo alpha 1-acid glycoprotein, a protein known to bind to hepatic asialoglycoprotein receptors, dramatically extended the intravascular survival time of asialo C1-INH. In agreement with the observations on other plasma glycoproteins, these results indicate that desialylation of C1-INH results in rapid clearance by hepatic asialoglycoprotein receptors.

Characterization of beta-galactosidase from a special strain of Aspergillus oryzae.

beta-Galactosidase [EC 3.2.1.23] was isolated from a partially purified preparation obtained from cultured cells of a special strain of Aspergillus oryzae, RT 102 (FERM-P1680). The enzyme preparation gave a single protein band on polyacrylamide gel electrophoresis and was free from alpha-galactosidase, alpha- and beta-mannosidase, alpha- and beta-N-acetylhexosaminidase, and protease activities. The beta-galactosidase was capable of acting on aryl beta-galactosides, lactose, and lactosides. It also hydrolyzed beta-galactosyl linkages in urinary glycoasparagines and asialo alpha1-acid glycoprotein. The enzyme was rather stable in aqueous solution, retaining full activity at 4 degrees for at least several months. At pH 4.5, the optimum pH for the enzyme activity, and 37 degrees, full activity was maintained for several days.

Isolation and characterization of jack bean beta-galactosidase.

A simple procedure has been devised to isolate beta-galactosidase from jack bean meal. The final preparation gives one major protein banc in disc gel electrophoresis. The substrate specificity of this enzyme toward some natural oligosaccharides, glycoproteins, and sphingoglycolipids has been examined in detail. Among three isomers of N-acetyllactosamine, Galbeta1leads to4GlcNAc; while Galbeta1leads to3GlcNAc was hydrolyzed very slowly. This property can be used to distinguish the galactose linkage in asialo-GM1 (Galbeta1leads to3GalNAcbeta1leads to4Galbeta1leads to4Glcleads toCer) and that in lacto-N-neotetraosylceramide (Galbeta1leads to4GlcNAcbeta1leads to 3Galbeta1leads to4Glcleads toCer). For hydrolyzing glycolipids, the effect of sodium taurodeoxycholate and sodium taurochenodeoxycholate on the rate of hydrolysis was carefully examined. This enzyme hydrolyzes lactosylceramide and asialo-GM1 faster than GM1. These results suggest that in addition to the type and linkage of the penultimate sugar unit, the sugar unit at the distal position of the saccharide chain also affects the hydrolysis rate. It also readily liberates 80% D-galactosyl units from asialo alpha1-acid glycoprotein. Escherichia coli beta-galactosidase on the other hand cannot hydrolyze asialo-alpha1-acid glycoprotein, lactosylceramide, GM1, asialo-GM1, and lacto-N-neotetraosylceramide. The molecular weight of this enzyme is about 75,000 and the isoelectric point is pH 8.0. With p-nitrophenyl beta-D-galactopyranoside as substrate, optimal activity occurs at pH 2.8 with glycine-HCl buffer and at pH 3.5 with citrate-phosphate buffer. With lactose as substrate, the pH optimum in these two buffers are 2.8 and 4.0, respectively. Km values for p-nitrophenyl beta-D-galactopyranoside, o-nitrophenyl beta-D-galactopyranoside and lactose are 0.51 mM, 0.63 mM, and 12.23 mM, respectively. Many inhibitors for this enzyme including inorganic ions, monosaccharides, and glycosides are investigated. In contrast to E. coli beta-galactosidase, jack bean beta-galactosidase is not inhibited by p-aminophenyl thio-beta-D-galactopyranoside.