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

The mucins of sheep colonic mucosa, like other epithelial secretions, are members of the group of 'neutral' niucosubstances (Werner, 1953; Kent, 1962). These characteristically contain L-fucose, D-galactose, N-acetylamino sugars and frequently sialic acids and mannose (Gottschalk, 1960). Their chemical structure and the nature of the sugarpeptide links involved have not yet been established. Previous investigations (Pasternak, Kent & Davies, 1958; Pasternak & Kent, 1958) have shown that mucosal cells, as scrapings in vitro, were highly active in incorporating [3nS]sulphate into the mucins of various gastrointestinal tissues. Wolf & Varandani (1960) and Wolf, Varandani & Johnson (1961) described partly purified enzyme systems from rat and pig colonic tissues, which catalysed the incorporation of isotopically labelled sulphate. In addition, homogenates incubated with [14C]glucose gave radioactive mucins, from which [14C]glucosamine could be isolated after acidic hydrolysis. A detailed investigation of the conversion of glucose into glucosamine in this tissue has been made by Pasternak (1961). Evidence was presented by Wolf & Varandani (1960) and by Wolf et al. (1961) that the sulphated constituent of their mucin preparations resembled chondroitin sulphate. This acidic mucosubstance had been reported to occur in stomach tissue by Smith, Gallop, Harris-Smith & Stanley (1952) and by Smith & Gallop (1953). That the mucosubstances of intestinal secretions