Biosynthesis of intestinal mucins. 4. Utilization of [1-14C]glucose by sheep colonic mucosa in vitro

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Abstract
Incubation of surviving sheep colonic mucosal serapings in oxygen with [1-C14]glucose results in labelling of the mucosubstances. L-Fucose did not inhibit this incorporation. The papain-digested C14-labelled mucosubstances, analysed by zone electrophoresis, consist of 2 nearly-related C14-labelled mucopoly-saccharides and unlabelled nucleic acids (RNA and DNA). The nucleic acids can be removed by fractionation in Rivanol(6,9-diamino-2-ethoxy acridine lactate)-ammonium formate. Acidic hydrolysis of the C14-labelled mucopolysaccharides gave C14-labelled sialic acid, galactose, glucosamine and galactosamine, fucose and possibly mannose, containing 6, 11, 8, 4, 7 and < 1% of the total incorporated radioactivity respectively. Scrapings incubated with [S35]sulphate gave, on digestion with papain, s35-labelled mucin and no other non-diffusible radioactive components. Alkali digestion gave a mixture of radioactive products, including one more acidic than the mucin. Alkali treatment of the papain-digested mucin did not yield this acidic component. Papain digestion with non-radioactive mucin and C14-labelled protein from Escherichia coli did not produce a radioactive mucin product.