Serum mucoproteins

A Crystalline Serum Mucoprotein with High Cholinesterase Activity, R. Bader, F. Schultz, and M. Stacey,Nature, 154(1944) 183-184. 

Since antibodies occur in the globulin fraction of serum one predicts that the investigation of the fine structure of serum mucoproteins will become a problem of urgent immunological significance. It is doubtful however whether the carbohydrate group of mucoproteins can influence their immunological specificity.1 ... 

The physiological significance of mucoproteins in serum is unknown but it is tempting to speculate that they may simply be intermediate stages in the synthesis of albumins and globulins. However, it will be seen below that mucoproteins with hormone properties can be isolated from serum of pregnant mares, and that the enzyme choline esterase, is probably a serum mucoprotein. 

Rimington and Rowlands165 have isolated an extremely active preparation from the serum of pregnant mares. This material was obtained in a high degree of purity and was shown to contain hexose and hexosamine in the molar ratio of 2/1. In the fractionation it appeared that, at first, the hexose content decreases as the potency is raised, but later this trend is reversed. It was shown that hexose content could not be taken as indication of gonadotropic activity. The hexose/hexosamine ratio was 2/1 as in normal serum mucoproteins, so that this gonadotropic hormone may be a modified serum mucoprotein. 

By a careful fractionation of normal horse serum, involving as an essential part of the process a separation of closely related substances by the Schtitz168 foam technique, Bader, Schiitz and Stacey16 obtained a crystalline mucoprotein with high choline esterase activity. This appears to be the first mucoprotein obtained without the use of heat or alcohol, and while it is not yet claimed that the crystalline material is indeed the enzyme itself, arguments are advanced to show that the enzymic activity is closely bound up with mucoprotein structure. 

The considerably increased (20-40-fold) excretion of acid mucopolysaccharides suggests that Marfan s syndrome also represents a defect in the metabolism of connective tissues (B4). The major mucopolysaccharides excreted were indistinguishable in their electrophoretic mobilities from hyaluronic acid and chondroitin 4- or 6-sulfate. Examination of the levels of mucoproteins and acid mucopolysaccharides in the serum of cases of Marfan s syndrome revealed an increase in the latter, while the former is decreased. Bacchus (B1) considers that this pattern might be of clinical and pathogenetic significance. 

Gastric secretion represents a very complex naixture of electrolytes, water, carbohydrates, proteins, peptides, and amino acids, which are partly in solution and partly in more or less stable suspension. The large molecular materials of gastric secretion include enzymes, mucosubstances, serum proteins, peptides and products of proteolytic degradation of gastric proteins and mucoproteins, and blood group substances. 

DL-Hexose-hexosamine type serum mucoprotein (protein, mannose, galactose, hexosamine)... 

The latter group (M13, M14) separated two types of KIK factor from cancerous gastric juice. The first was a mucopolysaccharide and the second a mucoprotein. Others thought it to be a mucopolypeptide. A similar factor from cancerous ascitic fluid (19) contained 50-60% hexoses, 1.5% tyrosine, and 10% protein by biuret reaction. It formed a single peak at pH range 1.5-10.0 on paper electrophoresis, and at pH 8.6 moved with the mobility of serum y-globulin. 

G54. Glass, G. B. J., Rich, M., and Stephanson, L., Comparative study of serum and gastric mucoproteins. Federation Proc. 16, 46-47 (1957). Abstr. 

Electrophoretic evaluation of the mucous substances of the gastric juice is complicated by the somewhat similar electrophoretic mobilities of serum proteins and their degradation products. Serum albumin has a mobility only slightly more negative than that of mucoprotein in M2 (Fig. 4). The first anodic degradation product of albumin has a mobility identical with that of component M3a (Fig. 4). The second anodic degradation product of serum is localized on the electrophoretic partition very close to component M3b (Fig. 5). Finally, the mobility of y-globulin is identical with that of component XI. 

Fig. 24. Immunoelectrophoresis of human gastric juice. Immunoelectrophoietic patterns A, in vitro depepsinized normal gastric juice B, crystalline human pepsin C, crystalline human gastricsin D, human serum albumin E, glandular mucoprotein F, mucoproteose C, rapid vitamin Bj2 binder H, slow vitamin B 2 binder. Anti-gastric juice immune serum was used throughout. From Simons and Grasbedc (S9).

The mucin of the submaxillary gland appears to contain two mucoproteins. One js a n-glucosamine-di-n-mannose complex similar to that in the serum proteins, while the other is claimed to be a crystalline substance CuHjsOuN, containing D-glucosamine, two acetyl residues and a polyhydroxy acid which is not a uronic acid. It appears to be a type of sulfate-free chondroitin. 

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