Mucoprotein dissolved

When 1.5 volumes acetone is added to the trichloroacetic acid filtrate of the gastric juice, an abundant flocculent precipitate forms, which contains all the components of dissolved mucin with the exception of soluble mucus. If this precipitate is taken up in dilute alkali and then acidified with dilute HCl down to pH 3.5, a fine flocculent precipitate forms, which we named dissolved mucoprotein (G27, G36). It was later renamed glandular mucoprotein (G9, G38) because of its close relationship to the fundic glands of the stomach. This material contained much protein its nitrogen content was 12.61 0.44% and its tyrosine content 7.50 0.65% by the Folin-Giocalteu reaction. The reducing substance content was 6.38 1.48% before and 12.5% after hydrolysis (G9, G27, G36) (see Table 4). Werner (W9) determined the composition of this mucoprotein fraction and found that it contained 11.2% N by Kjeldahl, 8.8% hexosamine, 4.8% uronic acid, and 2.0% sialic acid. 

In 1961, Schrager (SIO) found a correlation between the mucoprotein and pepsin concentration in gastric juice and concluded that the dissolved mucoprotein represents just pepsin. Schrager s conclusion represents a gross oversimplification of a complex biochemical problem, which does not take note of contributions of the last 12 years made in this area. As far back as 1950 we demonstrated, in collaboration with Pugh and Wolff (G52), that some correlation does exist between the concentration of the mucoprotein and pepsin in gastric juice. But that this was an... 

When we processed dissolved mucoprotein in 1955 from gastric juice of various human subjects, and under conditions of variable stimulation, this material showed some variations in protein and hexose contents. Therefore, we stated at that time When we looked for explanation of these variations by elution of the paper electrophoretic strips, we found that the leading fast boundary corresponding to glandular mucoprotein contained much pepsin. This pepsin apparently has been inactivated... 

This third fraction of the dissolved mucin is precipitated by acetone from the supernatant, after removal of dissolved mucoprotein from the solution (G26, G27, G36). The material forms a resin-like and clumping heavy precipitate, which, on drying, is an amorphous chalky white... 

Following this, the dissolved mucin was further fractionated in our laboratory by isoelectric precipitation of the dissolved mucoprotein fraction from its alkaline solution lowering pH < 3.5, leaving the second dissolved mucin fraction, mucoproteose, in solution (G27). The details of this fractionation technique are shown in Figure 19. 

G25. Glass, G. B. J., and Boyd, L. J., Response of gastric dissolved mucoprotein to insulin A new test for evaluation of secretory status of fundal glands and integrity of nervous pathways to the stomach. Bull. N. Y. Acad. Med. 25, 459-460 (1949). 

G36. Glass, G. B. J., Boyd, L. J., Heisler, A., and Drekter, I. J., Studies on dissolved mucin of the gastric juice. III. Heterogeneity of the gastric dissolved mucin and its differentiation and separation into two main fractions Dissolved mucoproteose and dissolved mucoprotein. Bull. N.Y. Med. Coll. Flower Fifth Ave. Hosp. 2, 8-48 (1948). 

Some time ago we determined total dissolved mucin and its fractions during fasting and after alcohol test meals, histamine injection, and i.v. insulin in gastric juices of 60 patients with peptic ulcer and 106 controls with various gastric disorders (G30), In each of the 841 gastric specimens, the total dissolved mucin and its two fractions (mucoprotein and... 

The existence of more than one mucoprotein in the dissolved mucin fraction of the gastric juice was further substantiated in our laboratory (G26, G27, G36). We found (G27) that the composition of dissolved mucin varied markedly, depending upon the stimulus applied to gastric secretion. These variations included degree of hydration, extractability with 60% alcohol, and content of tyrosine, nitrogen, and reducing substances. We therefore postulated that, in man, at least two but probably three different mucous substances were present within the mixture of mucosubstances called dissolved gastric mucin (Gll, G27) (Fig. 16). 

Similar inferences were drawn regarding dissolved mucin from dog stomach by Grossberg et al. (G70), who determined hexosamine and lu-onic acid contents of canine gastric juice and mucus before and after histamine and sham feeding. Determinations were performed after acid hydrolysis and showed marked variations in the mutual ratio of these two components, depending on the nature of the stimuli applied. This suggested the existence of at least two different kinds of mucoprotein in these secretions—one containing uronic acid, and the other hexosamine with or without small amounts of the former (Fig. 17). 

Hexosamine to Tyrosine Ratio in Mucoprotein H (= Mucoproteose) and Mucoprotein V (= Glandular Mucoprotein) Fractions of Dissolved Gastric Mucin Collected Under Similar Conditions from Heidenhain Pouches of 4 Docs... 

Pugh et al. (P7) and Mack et al. (Mia, M2), using free boundary electrophoresis, showed that mucoprotein and mucoproteose fractions of the dissolved mucin (G5) had different electrophoretic mobilities mucoprotein fast anodic mobility (5.5-6.9 X cm sec volts ), mucoproteose slow anodic mobility (0.5-1.0 X cm sec volts ) in veronal buffer of pH 9.2 (Fig. 1). Soluble mucus had intermediate mobility of — 3.5 X 10 . It was also noted by Mack et al. (Ml) that the mucoprotein fraction processed from the acid human gastric juice, when nm by itself on Tiselius electrophoresis or when added to acid gastric juice, did not have as fast mobility as the fastest anodic component of the gastric juice, which had a mobility of 7.4-7.S X cm sec volts and which probably, as we know now, corresponded to the complex of pepsin and mucoprotein (see G5). 

Norpoth et al. (N3) compared electrophoretic patterns oi mucoprotein and mucoproteose with those of various other fractions precipitated from the gastric juice. When gastric juice was precipitated by Martin s method (see G5) the gastroglobulin, which is similar to dissolved mucin, showed two peaks which had electrophoretic localization of the glandular mucoprotein and mucoproteose fractions, respectively. Collodion filtration of... 

Kawarada (see BIO) determined polarographic waves of mucus and dissolved mucin fractions, i.e., mucoprotein and mucoproteose. Direct correlation was established between HCl concentration and polarographic mucin waves. In gastric cancer, the polarographic wave of mucoprotein disappeared while that of mucoproteose increased. In peptic ulcer, no significant changes were found. 

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