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

A novel esterase has been isolated from bovine plasma in a highly purified form. According to electrophoresis and ultracentrifugal sedimentation patterns it represents a homogeneous 7.1 S sialoglycoprotein being composed of 5.9% neutral carbohydrates, 4.8% aminosugars and 4.4% sialic acid. In catalytic amounts it normalizes the prolonged clotting time of plasma deficient in Hageman factor and exhibits a strong esterase activity towards $\text{N-}\text{benzoyl-}\text{l}\text{-arginine}$ ethyl ester.

The glycosaminoglycans in fracture callus from rabbits have been isolated, and analysed with chemical and physical methods. Hyaluronic acid as well as chondroitin sulphate with infrared characteristics of both -4-sulphate and -6-sulphate were found. When callus of different degrees of maturation was studied, differences in the recovery of the total glycosaminoglycans as well as differences in the ratio between the recovered fractions were found, probably reflecting the different morphology of fracture callus of different ages.

• 1.

  1. The interactions of poly-l-lysine with soluble erythrocyte components and with Collocalia mucoid, a sialoprotein of avian origin, were studied by electrophoresis and immuno-electrophoresis in agar gel.

• 2.

  2. Polylysine combined with erythrocyte membrane glycoprotein and with Collocalia mucoid to form visible precipitates in agar gel; erythrocyte fractions devoid of glycoprotein failed so to react.

• 3.

  3. A precipitate of virus receptor substance with polylysine could be quantitatively redissolved by the addition of poly-l-aspartic acid to the mixture. Whether this change in solubility occurred as a result of displacement of polylysine from the glycoprotein or by the formation of soluble complexes could not be established.

• 4.

  4. Neuraminidase (EC 3.2.1.18) treatment of erythrocyte glycoproteins and Collocalia mucoid greatly reduced or abolished their capacity to precipitate with polylysine.

• 5.

  5. The findings suggest that N-acetylneuraminic acid in the acid glycoprotein of erythrocyte membranes is an important factor in the agglutination of erythrocytes by polybases, a phenomenon thought to have some bearing on intravascular thrombus formation.

OSM prepared from sheep is known to contain O-glycosidic linkages involving the reducing group of N-acetylgalactosamine and the hydroxyl groups of serine and threonine. It is the aim of this paper to establish whether or not in addition to this linkage another type of alkali-labile linkage, in particular a glycosidic-ester linkage, is present in OSM.

In the first set of experiments it was found that the release of 35.2% of N-acetylgalactosamine, when OSM was kept at pH 8.0 and 42° for 120 h, was matched by the loss of an equimolar amount of serine and threonine without a significant change in the other amino acids. In a second set of experiments it was shown that on treating OSM with 0.1 N NaOH at 4° the decrease of bound hexosamine with time was linear. Finally, glycopeptides prepared by trypsin (EC 3.4.4.4) or pronase action on OSM were treated with LiBH₄ in tetrahydrofuran. No significant difference in the dicarboxylic amino acids before and after such treatment was observed. Only traces of homoserine and α-amino-δ-hydroxy-n-valeric acid were detectable after LiBH₄ reduction.

Since the LiBH₄ treatment of trypsinized OSM prepared from Australian sheep resulted in the loss of 35% of the dicarboxylic acid content, the suggestion is made that the fine structure of the ovine submaxillary glycoproteins may vary with the age of the animals. In Australia, lambs of an average age of 4 months were used for the work; in Europe only sheep of three years or more are slaughtered. Similar differences with age have been described for the fine structure of the chondroitin sulphates composing human hyaline cartilage.