Biochimica et Biophysica Acta (BBA) - Specialized Section on Mucoproteins and Mucopolysaccharides最新文献

An acid mucopolysaccharide preparation was isolated from rat kidneys. Its major amino sugar component was glucosamine, with only minor amounts of galactosamine. It contained sulphate, gave a positive carbazole reaction for uronic acids with a high carbazole: orcinol ratio, and possessed anticoagulant activity. The preparation could be further fractionated with the aid of cetyl pyridinium chloride, and by chromatography on columns of Ecteolal-cellulose and DEAE-Sephadex. From these studies it was concluded that the major component of the mucopolysaccharide preparation was a heparin-like substance, and that hyaluronic acid was present as a minor component. Since mucopolysaccharides containing galactosamine were found only in small quantities, it appears that rat kidneys do not contain significant amounts of chondroitin sulphates.

• 1.

  1. The isolation and characterization of a protein fraction from the electric organ of Electrophorus electricus is described. The protein was a material of relatively low molecular weight. It was soluble in water, dilute base and dilute acid and had many of the characteristics of mucoproteins.

• 2.

  2. Analytical studies revealed the presence of galactose, N-acetylgalactosamine, glucuronic acid and of N-acetylneuraminic acid. Evidence is presented which indicated, however, that the carbohydrate constituents did not occur as a single polysaccharide moiety. The protein or polypeptide moiety apparently does not contain any of the aromatic amino acids.

• 3.

  3. Physical studies of the isolated sialoprotein reveal marked polyanionic characteristics. Dye-binding and dye-displacement studies as measured by fluorescence quenching demonstrated that “receptor-like” function was simulated by this materiall. It was concluded, however, that this particular sialoprotein, in the form isolated, merely showed ion-exchange capabilities and lacked the high degree of specificity postulated for biological receptors.

κ-Casein was hydrolyzed with either crystalline papain (EC 3.4.4.10) or Pronase P. The products of hydrolysis were fractionated by means of ion exchange and Sephadex G-25. A carbohydrate-rich macropeptide isolated from the papain digest contained 4–5 times the quantities of hexose, hexosamine and sialic acid that were present in κ-casein. The concentrations of the three saccharides bore approximately the same ratio to each other in κ-casein as they did in the macropeptide fraction. These results suggested that the carbohydrate part of κ-casein may be a prosthetic group containing hexose, hexosamine and sialic acid in the ratio of 1:1:1. The macropeptide fraction isolated from the Pronase-P hydrolyate contained approximately double the quantity of carbohydrate that was present in the macropeptide isolated from the papain digest.

The hydrolysis of chitin in solution in strong HCl was studied over a range of acid concentration and temperature. The data suggest that the rate of hydrolysis governed by the structure of the chitin. A simple procedure for the isolation of the oligosaccharides obtained from chitin was developed, for use in the preparation of low-molecular-weight substrates for lysozyme (N-acetylmuramide glycanohydrolase, EC 3.2.1.17). Experiments studying the lysozyme-catalyzed hydrolysis of these oligosaccharides showed a large effect of chain length upon the rate of hydrolysis, and no effect of ionic strength.

The 6-sulfates of N-acetylglucosamine and N-acetylgalactosamine were synthesized using triethylamine-N-sulfonic acids as the sulfating agent. The products of the reaction were purified by fractionation on an anion-exchange column, desalted by means of an ion-retardation resin and converted to the barium salts by passage through the barium form of a cation-exchange resin. Evidence for the homogeneity of the 6-sulfates was provided by chemical analysis, paper chromatography. electrophoresis, colorimetric assay and infrared spectra. Proof for the position of the sulfate group on the primary hydroxyl of the N-acetylhexosamines was provided by periodate consumption studies, the detection of glycolaldehyde sulfate as an end product of periodate oxidation and comparison with a sample of N-acetylglucosamine 6-sulfate synthesized by an unambiguous route. The latter product was prepared via the 6-trityl intermediate as described in the text.