INTERCELLULAR MACROMOLECULES CONTAINING POLYSACCHARIDES

A survey is presented of the carbohydrate of intercellular spaces that is known to exist in the form of polysaccharide. This amounts to considering the polysaccharides made by connective tissue cells. The chemical structures of these polysaccharides are discussed in the cases in which they are known and regularities in patterns are noted. Such regularities make of these polysaccharides a natural group that may be related to the natural group of connective tissue cells that produce them. Viscosity is discussed as an important property of hyaluronate. The polyelectrolyte properties of these polysaccharides are considered in detail mainly from the point of view of their use in studying the polysaccharides, fractionating them, and accounting for their behavior in tissues. Polyelectrolyte properties are considered in connection with simple cations, micellar detergent cations, metachromatic dye cations, and protein cations. The existence of the polysaccharides in native tissues as compounds with proteins is discussed in detail, and with particular reference to the two cases most thoroughly studied, the chondroitin sulfate of cartilage and the hyaluronate of synovial fluid. A sharp distinction is drawn between compact and diffuse macromolecules by a contrast of tropocollagen and hyaluronate. The known proteinpolysaccharides of intercellular space are diffuse molecules. Experiments are described to show how hyaluronate hinders sedimentation, excludes compact macromolecules, or entangles with fibrils. Binding of water by connective tissue and elasticity of cartilage may be related to the tissue content of such diffuse macromolecules.

GROUP-SPECIFIC CARBOHYDRATE OF GROUP C-VARIANT HEMOLYTIC STREPTOCOCCI

The trypsinized cell walls of Group C hemolytic streptococci are composed of the specific carbohydrate antigen and a mucopeptide matrix. Certain phage resistant strains of Group C streptococci, isolated from organisms which survive exposure to Group C bacteriophage also possess carbohydrate and mucopeptide fractions, but the carbohydrate gives a precipitin reaction with Group A-variant antiserum and not with Group C antiserum. These strains have been termed Group C-variant. The C-variant carbohydrate contains 86 per cent rhamnose and only 2 per cent galactosamine, and is thus chemically and immunologically similar to Group A-variant carbohydrate. The evidence suggests that the antigenic determinants of Groups A-variant and C-variant carbohydrates are rhamnose-rhamnose linkages. These results strongly support the hypothesis that the carbohydrates of Groups A and C streptococci are composed of a similar rhamnose moiety but that the determinant amino sugar terminal to the rhamnose-rhamnose linkages in the case of Group A is N-acetylglucosamine whereas that of Group C is N-acetylgalactosamine.

CHARACTERISTICS OF AN IMMUNE SYSTEM COMMON TO CERTAIN EXTERNAL SECRETIONS

The gamma(1)A present in saliva and colostrum exists largely in the form of higher polymers, the major component of which has a sedimentation coefficient of 11S. The 11S gamma(1)A in these fluids differs from the polymers found in normal and myeloma sera both immunologically and by the fact that their sedimentation coefficients are unaffected by disulfide bond reduction in the absence of urea. However, like other gamma-globulins the 11S gamma(1)A molecules consist of multiple polypeptide chains linked by disulfide bonds. Local synthesis of gamma(1)A in the salivary gland has been shown by fluorescent and autoradiographic studies, although the fraction of the total salivary gamma(1)A which is derived from local production is uncertain. No evidence of transport of intravenously administered I(131)-labeled 7S gamma(1)A from serum to saliva was obtained. Immunological specificity has been demonstrated in the salivary and colostral gamma(1)A. Whether that portion of the gamma(1)A which is immunologically specific is a piece incorporated during the local synthesis of gamma(1)A in the gland or is added by the epithelial cell in the process of transport remains to be determined. Antibody activity (isohemagglutinins) have been demonstrated in saliva and colostrum and have been shown to be of the gamma(1)A-type. In both of these fluids activity is associated primarily with gamma(1)A-polymers of 11S and 18S sizes. There appears to be an immunological system which is characteristic of certain external secretions. Its properties including the local production of a distinctive type of antibody separate it from the "systemic" system responsible for the production of circulating antibody. This system may play a significant role in the body's defense mechanisms against allergens and microorganisms.

THE RELATION OF INFLAMMATION TO THE MOLECULAR STRUCTURE OF CARBON COMPOUNDS SOLUBLE IN THE FLUIDS OF THE BODY

The peritoneal, like the pleural cavity, gives opportunity to measure with adequate accuracy the activity of inflammatory reactions defined by movement of fluid within the cavity, by migration of leucocytes into it, and by exudation of proteins from the plasma. The activity of inflammatory reactions caused by saccharides or by alcohols that were tested varied in accord with their molecular weight, the osmotic pressure maintained by solutions of corresponding concentration, their boiling point, or by other colligative properties. Blood serum or globulin in the concentration with which it occurs in blood serum injected into the peritoneal cavity caused changes which differed little from those caused by physiological salt solution. Protein with molecular weight as low as that of cytochrome C (12,000) or ovalbumin (45,000) when in dilute solution (1 per cent) were rapidly absorbed, whereas trypsin and chymotrypsin under the same conditions caused very active inflammatory reactions because they set free amino acids and perhaps polypeptides with amino acids in short chains. The activity of inflammatory reactions caused by carbon compounds soluble in body fluids varied in accord with their colligative properties.

THE PHOTOASSIMILATION OF SUCCINATE TO HEXOSE BY RHODOSPIRILLUM RUBRUM

1. A pathway for the synthesis of hexose from succinate by Rhodospirillum rubrum is proposed. 2. With 2,3-(14)C(2)-labelled succinate and fumarate as substrates in experiments with chromatophores and a soluble enzyme fraction of R. rubrum it was found that the products of succinate metabolism by the extracts were the same as in whole cells. It was also found that the light-dependent oxidation of succinate was catalysed by the chromatophores, but that all the other enzymes involved were in the soluble fraction. 3. By using specific assays the presence of all the enzymes required for the proposed pathway was demonstrated in the extracts and their specific activities were measured. 4. The overall rate of succinate assimilation was measured manometrically. The activities of the enzymes assayed were sufficient to account for the overall rate of assimilation. It is concluded that the proposed pathway represents the major mechanism for synthesis of hexose from succinate in R. rubrum. 5. The formation of alanine and aspartate was observed in experiments with isotopically labelled substrates, and possible synthetic pathways for these compounds are discussed.

THE CARBOHYDRATE-POLYPEPTIDE LINKAGES, THE AMINO ACID SEQUENCES OF THE PEPTIDES ADJACENT TO SOME OF THESE BONDS, AND THE COMPOSITION AND SIZE OF THE CARBOHYDRATE UNITS OF ALPHA-1-ACID GLYCOPROTEIN

1. The glycopeptides derived from a proteolytic digest of sialic acid-free alpha(1)-acid glycoprotein were separated on a DEAE-cellulose column into five main fractions. 2. The average molecular weight of these glycopeptides was 2400, except for one fraction whose molecular weight was 3100. The average molecular weight of the sialic acid-free carbohydrate units was found to be 2200. From these data and the carbohydrate content of the native protein and the assumed molecular weight of 44000, it was concluded that alpha(1)-acid glycoprotein probably possesses five carbohydrate units. The sialic acid-containing carbohydrate units of this glycoprotein have an average molecular weight of 3000, except for one unit the molecular weight of which is significantly higher. 3. The N-, non-N- and C-terminal amino acids of the main glycopeptides were determined. Aspartic acid and threonine occur in most peptides. Alanine, glycine, proline, serine and lysine were present in varying amounts. Traces of other amino acids were also found. 4. The amino acid sequence of three main glycopeptides was established and indicated that these glycopeptides are located at different positions of the polypeptide chain of the glycoprotein. These sequences are: Asp(NH(2))-Pro-Lys; Thr-Asp(NH(2))-Ala; Asp(NH(2))-Gly-Thr. 5. From the results of a series of chemical reactions (periodate oxidation, hydrazinolysis, dinitrophenylation, mild acid hydrolysis) it was shown that the hydroxyl group of the N-terminal threonine and the in-amino group of lysine are free and that the beta-carboxyl group of aspartic acid is present as amide. It was concluded that this amide group is involved in the carbohydrate-polypeptide linkages of at least four carbohydrate units of alpha(1)-acid glycoprotein. 6. The carbohydrate composition of the sialic acid-free glycopeptides was determined in terms of moles of neutral hexoses, glucosamine and fucose/mole. 7. Fucose, at least to the larger part, is not linked to sialic acid, and its (glycosidic) linkage is significantly more stable toward acid hydrolysis than the bond of the sialyl residues. 8. Heterogeneity of the carbohydrate units of alpha(1)-acid glycoprotein was found with regard to size and to content of fucose and sialic acid.