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

Uridine diphosphoacetylglucosamine is shown to undergo a hydrolytic cleavage by an enzyme present in sheep brain. The products of the reaction are identified as N-acetylglucosaminei-phosphate and UMP. The enzyme responsible for this degradation has a wide distribution in the tissues of the rat. ATP, UTP, ADP and N-acetylglucosaminei-phosphate act as powerful inhibitors of this enzyme. The enzyme requires Co²⁺ for its maximal activity. It shows a broad optimal range of pH from 8–9. The enzyme preparation cleaves uridine diphosphoglucose and uridine diphosphoglucuronic acid to lesser extents than uridine diphosphoacetylglucosamine.

A new acidic polysaccharide which produces an immunogenic response in mice, dogs and man has been obtained in pure form from acid hydrolysates of Staphylococcus aureus cells. Structural studies show the antigen to be composed of d-glucosaminuronic acid and l-alanine with O- and N-acetyl substitution.

Chick embryo somites, Stages 16–17, when grown in vitro with embryonic notochord or spinal cord, form cartilage, in contrast to somites grown in the absence of notochord or spinal cord.

In a study of this system of embryonic induction, cell-free extracts of both types of cultures were examined for the presence of ATP-sulfurylase (ATP:sulfate adenylyl-transferase, EC 2.7.7.4) and adenosine-5′-phosphosulfate kinase (ATP:adenylylsulfate 3′-phosphotransferase, EC 2.7.1.25). Both enzymes were demonstrated in the somites stimulated with notochord by the ability of the enzymic preparations to form 3′-phosphoadenosine-5′-phosphosulfate from ATP, Mg²⁺ and ³⁵SO₄₂^-. Formation of 3′-phosphoadenosine-5′-phosphosulfate was not detected in somites cultured without notochord.

3′-Phosphoadenosine-5′-phosphosulfate generated by extracts of cartilage-forming somites was characterized by electrophoretic and chromatographic behavior, lability to mild acid, ability to serve as substrate with rabbit-liver sulfokinase (3′-phosphoadenylylsulfate: phenol sulfotransferase, EC 2.8.2.1), and the formation of adenosine 5′-phosphosulfate after incubation with alkaline phosphatase (orthophosphoric monoester phosphohydrolase, EC 3.1.3.1).

Cell-free extracts were also prepared from tissues which were isolated from the embryo but not cultured. These extracts of somites, notochords and spinal cords, and mesonephri had no demonstrable activity for ATP-sulfurylase and adenosine-5′-phosphosulfate kinase. Cell-free preparations from the whole trunk, however, showed considerable activity for these enzymes.

d-[i-¹⁴C]Glucosamine was administered to rats and rabbits by intraperitoneal injection in order to study the incorporation of hexosamines into the glycoproteins of liver and serum. Maximum radioactivity of the fraction soluble in trichloroacetic acid was found in rat livers within 30 min after injection and in rabbit livers within 1 h. Highest values for radioactivity in the trichloroacetic acid-insoluble fraction were found at 3 h for the rat. Maximum protein-bound radioactivity in the serum was found at 3 h for the rat and at 7 h for the rabbit. Efficient incorporation into serum proteins was found in both species, being 24 % and 28 % of the administered dose for rats and rabbits, respectively, at the maximum level of radioactivity. About 22 % of the bound radioactivity of serum was found associated with sialic acid in the rat, most of the remaining 78 % was associated with glucosamine, and only negligible amounts of radioactivity were found in the hexoses. Liver glycogen was not radioactive. Glucosamine was isolated from serum protein hydrolysates with the radioactivity in the number-one position. Therefore, it appears that parenterally administered glucosamine is incorporated into liver and tissue glycoproteins without degradation. The value of [i-¹⁴C]glucosamine as a tool for further studies of glycoprotein metabolism is indicated.

Purified chondroitin sulfate prepared from shark cartilage (chondroitin sulfate C) was desulfated and esterified with methanolic HCl. Chondroitin methyl ester (II) was reduced with NaBH₄ to give carboxyl-reduced chondroitin (III), which was submitted to hydrazinolysis to remove the acetyl group of the 2-acetamido-2-deoxy-d-galactopyranose moiety. The N-deacetylated carboxyl-reduced chondroitin (IV) was dyrolyzed with HCl and the hydrolyzate was passed down a Dowex-50 (H⁺) column. A disaccharide (V) and 2-amino-2-deoxy-d-galactopyranose adsorbed on the column were eluted with dilute HCl. Both the substances were N-acetylated and separated effectively by means of a cellulose powder column (Solvent B), and a novel disaccharide, ${}_4\text{-O-(β-2-}\text{acetamido-2-deoxy}\text{-}\text{d}\text{-}\text{galactopyranosyl}\text{)-}\text{d}\text{-}\text{glucopyranose}$ (VII), was isolated. The reducing end of the isolated disaccharide was reduced with NaBH₄ to give ${}_4\text{-O-(β-2-}\text{acetamido-2-deoxy}\text{-}\text{d}\text{-}\text{galactopyranosyl}\text{)-}\text{d}\text{-}\text{glucitol}$ (VIII). Acid hydrolysis of this substance gave d-glucitol (IX) and 2-amino-2-deoxy-d-galactopyranose (X), which were characterized by infrared spectra and by paper chromatography. The structures of these substances (VII, VIII) were confirmed by means of periodate oxidation.

Vertebral chondrocytes from 10-day-old chick embryos were examined after growth for five days in vitro and in vivo. The chondrocytes, including the hyaline matrix, from both methods of growth were extracted for glycosaminoglycuronoglycans and the partially purified polymers were analyzed for hexosamines. It was found that the chondrocytes, when removed from their cartilage matrix and grown in vitro, synthesized sulfated glycosaminoglycans which migrated in electrophoresis as chondroitin sulfates. The partially purified glycosaminoglycans were not, however, chondroitin sulfates since glucosamine was characterized as the major hexosamine. Neither galactose nor glucuronic acid were demonstrated as part of the glucosamine-containing polymer. The polymer was produced by the cells grown in vitro regardless of age or original location, dorsal or ventral, in the vertebral column. In contrast, chondrocytes which were grown in vivo for 10 or 15 days synthesized predominately a polymer which had characteristics of chondroitin 4- or 6-sulfate.