The metabolism of sialic acid in cystic fibrosis.

The activities of plasma and fibroblast cytidine 5'-monophosphate-sialic acid:glycoprotein sialyltransferases of patients with cystic fibrosis have been found to be within the range of activities of age- and sex-matched normal controls when asialofetuin served as the sialic acid acceptor. The use of desialylated preparations of purified human plasma alpha 2-macroglobulin, as an acceptor, demonstrated 35 to 52% reduction in the incorporation of sialic acid into the alpha 2-macroglobulin from patients with cystic fibrosis as compared to that of alpha 2-macroglobulin from normal controls. The reduced sialylation was dependent upon the source of the alpha 2-macroglobulin acceptor but independent of the source (cystic fibrosis or normal) of the sialyltransferase enzyme. Using radiolabeled precursors, the rates of the synthesis of N-acetylneuraminic acid from N-acetyl-D-mannosamine, the release of sialic acid from glycoproteins and the conversion of free sialic acid into CMP-sialic acid have been determined in cultured skin fibroblasts from patients with cystic fibrosis and found to be not significantly different from those of normal controls.