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

Physicochemical studies have been made of two different preparations of bone sialoprotein, a glycoprotein from bovine cortical bone, which contains a high proportion of sialic acid groups. Determinations have been made of s⁰_20,w, diffusion coefficient, molecular weight, sedimentation coefficient distribution, optical rotatory dispersion curves, mobility during free boundary electrophoresis, partial specific volume and refractive index increment. The two preparations differed slightly in molecular weight, but both are small molecules, polydisperse but homogeneous with respect to centrifugation and electrophoresis. Their frictional coefficients are higher than that expected for globular molecules and they have little or no helical content. The results are discussed in the light of available analytical and structural information.

• 1.

  1. Chemical and enzymological studies on neuramin-lactose sulfate have provided supporting evidence for the proposed structure: $\text{O-α-}\text{D}\text{-N-}\text{acetylneuraminyl}\text{-(2→3)-O-β-}\text{D}\text{-}\text{galactopyranosyl}$$\text{6-O-}\text{sulfate}\text{-(1→4)-}\text{D}\text{-}\text{glucopyranose}$.

• 2.

  2. The enzymological studies showed that neuramin-lactose sulfate is hydrolyzed by neuraminidase (EC 3.2.1.18) and that the lactose sulfate moiety of the molecule is resistant to the action of β-galactosidase (EC 3.2.1.23).

• 3.

  3. The chemical studies showed that during periodate oxidation of neuramin-lactose sulfate, the galactosyl moiety was protected, while in the case of lactose sulfate it underwent complete oxidation.

• 4.

  4. Synthetic D-galactose 6-O-sulfate and the galactose sulfate isolated from neuramin-lactose sulfate were found to be identical by paper chromatography, ionophoresis, infrared spectra and lack of formaldehyde production during periodate oxidation.

An examination has been made of a number of ovarian cyst fluid glycoproteins that are sparingly soluble water but are similar in general composition to the readily soluble blood-group specific glycloproteins obtained from the same source. Ultracentrifugal analysis of approx. 0.1% w/v solutions of the sparingly soluble materials indicate that they have much larger sedimentation coefficients (S_20,w) and molecular weights than have the water-soluble glycoproteins. The sparingly soluble substances have more total amino acids and proportionally more aspartic and glutamic acids and cystine and less serine and threonine than have the soluble glycoproteins. The sparingly soluble substances mostly dissolve in buffered (pH 6.8–7.0, 0.05 M) solutions of thioglycolate, sulphite or cysteine, reagents that bring about the scission of -S-S-bonds. The behaviour and properties of the sparingly soluble glycoproteins suggest that they arise through the building up of relatively small glycoproteins to larger macromolecules through the formation of -S-S- intermolecular associations. A number of ways whereby the formation of these sparingly soluble glycoproteins could occur are discussed.

The distribution of β-glucosidase (EC 3.2.1.21) in dormant and germinating conidia of Aspergillus oryzae has been studied. A considerable amount of the bound β-glucosidase is found in the conidia coats of dormant and germinating conidia, and the ratio of bound form to soluble form in the conidia increases as germination proceeds. The bound enzyme is not removed by detergents, EDTA, urea, salts, and β-1,3-glucanase, but sonication is fairly effective. The physical and chemical properties show that the bound enzyme is identical to the soluble enzyme.

Human diploid fibroblast strains and established mouse fibroblast lines continue to synthesize hyaluronate over many cell generations in culture. However, this property may be lost in the course of many years of serial culture of established lines as it is no longer detectable in three well-known mouse lines of fibroblastic origin, including L-cells. Transformation of the established mouse fibroblast line 3T3 by SV₄₀ or polyoma virus and of human diploid fibroblast strains by SV₄₀ leads in each case to a marked diminution in the rate of hyaluronate synthesis.

Incorporation of D-[1-¹⁴C]galactosamine into serum proteins and tissues of the rat was studied. After single intraperitoneal injections, about 20% of administered radioactivity was excreted in urine within 6 h. Only 1% was found in expired CO₂ at this time; 12% was found at 72 h. High levels of bound (non-dialyzable) radioactivity appeared first in liver and then in serum. Non-dialyzable radioactivity in serum was found associated with all electrophoretically separated fractions with the greatest concentration in the α-globulins. Hexosamines were separated by paper chromatography from serum protein hydrolysates; glucosamine had a ¹⁴C content over ten times that of galactosamine in a sample taken 6 h after injection. A progressive increase in non-dialyzable radioactivity with time was found in both connective tissue and the fluid from within stainless-steel wire mesh cylinders implanted subcutaneously 2 weeks prior to injection of [1-¹⁴C]galactosamine. Mucopolysaccharides, extracted from connective tissue, exhibited electrophoretic mobility and staining characteristic of chondroitin sulfate and hyaluronic acid. Although hyaluronic acid and chondroitin sulfate moieties were labeled to the same extent, their hydrolysates contained glucosamine with 4 times more radioactivity then galactosamine, possibly indicating the presence of a substance containing glucosamine in the chondroitin sulfate area. These results indicate that much of the galactosamine is converted to glucosamine. Radioactive galactosamine appears to be of value for metabolic studies of glycoproteins and mucopolysaccharides.

Several dialyzable, hydroxyproline-containing glycopeptides have been isolated from human aorta and gingiva, rat skin and guinea pig skin, and partially characterized. It is suggested that they may be associated with the metabolism of reticulin, or of the reticular fibers, of connective tissue.

An acid mucopolysaccharide preparation from the tail fins and back skin of Rana catesbeiana tadpoles has been isolated and fractionated. In both of these tissues at least 96% of the mucopolysaccharide preparation was found to be hyaluronic acid. The remaining 4% has not been fully characterized, but does not appear to be chondroitin sulfate B.