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

• 1.

  1. Protein material in 5% trichloroacetic acid extracts of human plasma appears physically homogeneous and closely resembles α₁-acid glycoprotein (orosomucoid). Molecular weight is estimated at 41000 (±2000), E_{1%,icm²⁷⁸} is 7.7, and the protein has a high carbohydrate and sialic acid content.

• 2.

  2. Concentrations of this protein are markedly elevated in renal insufficiency.

Thoracic and abdominal aortas from dogs were analyzed for their mucopolysaccharide content by a modification of existing methods. Acid mucopolysaccharides represented approx. 0.7% of the dry weight. The major components were chondroitinsulfuric acid A and C, with lesser amounts of heparitin sulfate and negligible amounts of hyaluronic acid and chondroitinsulfuric acid B.

Data are presented to show that the intrinsic viscosity of hyaluronic acid elaborated into the culture medium supportinf human connective-tissue cells in vitro is modulated in a systematic manner by the cells. Intrinsic viscosity is reduced during rapid cell division and by hydrocortisone treatment. Conversely, the initial lag phase of culture growth and colchicine treatment are attended by formation of hyaluronic acid with a high intrinsic viscosity.

• 1.

  1. In order to determine whether the collagen found in cartilage is synthesized by the same cells which synthesize chondroitin sulfate, ³H or ¹⁴C-labeled proline was administered to pure cultures of freshly liberated chondrocytes, and the synthesis of collagen was followed by the appearance of labeled hydroxyproline. The results indicated that the chondrocytes synthesized collagen

• 2.

  2. Double-label experiments with the chondrocytes indicated that the collagen synthesis occurred concurrently with sulfate incorporation.

• 3.

  3. The incorporation of [³⁵S]sulfate and synthesis of labeled hydroxyproline was also examined in the progeny of chondrocytes which were grown on fibrin clots for several generations. These “de-differentiated chondrocytes” did not incorporate [³⁵S]-sulfate or synthesize labeled hydroxyproline even though the rates of labeled proline incorporation were similar to those observed with freshly liberated chondrocytes.

• 4.

  4. The failure of de-differentiated chondrocytes to incorporate sulfate and to synthesize collagen suggests that the pathways for the synthesis of sulfated mucopolysaccharides and collagen may be closely interrelated.

Spore coats of Aspergillus oryzae have been mechanically isolated. They exhibited a complex chemical composition consisting of polysaccharide (mannose, glucose, galactose and glucosamine), phosphate, protein and nucleic acid. Spore coats were partially hydrolyzed by the lytic enzyme from Bacillus circulans, and glucose, laminaribiose and other unknown sugars were detected in the hydrolyzate. No qualitative differences were found between the cell walls and the spore coats. The major quantitative difference was in protein content, which was higher in the spore coats.

Incubation of rat-mammary-gland slices in a physiological solution containing [¹⁴C]glucose disclosed incorporation of radioactivity into both lactose and neuraminlactose. After 1 min incubation the labeling was restricted to the glucose moiety of these molecules while administering the glucose in vivo resulted in labeling of all components of these molecules after 3 h.

The specific activities of free lactose and lactose from neuramin-lactose are of similar order of magnitude in all experiments and, although these findings are compatible with the currently known biosynthetic pathways of these substances, the possibility of an alternate pathway involving the action of neuraminidase is suggested in connection with the rapid equilibration of the specific activities of these substances.

The sedimentation behaviour of two globular proteins of different size has been studied in solutions of polymers of varied structure. That the movement of the larger protein was in all instances retarded to a greater extent than that of the smaller indicated that the polymers investigated had a sieving effect. The ability of a polymer to inhibit the migration of another substance was demonstrated to increase with its degree of polymerization and decrease with branching. Charged substituents in a polymer were found to augment materially its effectiveness in restricting transport.

γ-Glutamyl transpeptidase preparations contain bound neuraminic acids which can be removed by treatment with neuraminidase (EC 3.2.1.18). The products of enzymatic digestion have been identified as N-acetyl- and N-glycolylneuraminic acids by paper chromatography. The activity of the enzyme is not affected by digestion with neuraminidase. The stability in acid solution is increased, and the electrophoretic behaviour and the sedimentation patterns are altered after treatment with the enzyme.