Properties of microsomal glycoprotein galactosyltransferase of cultured human fibroblasts in relation to cystic fibrosis

Effect of homeopathic dilutions on subcellular enzymatic activity

The activity of various inhibitors on several subcellular enzymes was studied. First we determined the inhibitory concentration required to reduce maximum enzymatic activity by 50%, then the effect of various hahnemannian dilutions of the same inhibitory agent was tested. Seven inhibitory agents were tested in this way on seven different enzymatic systems. No effects of these hahnemannian dilutions were shown.

Glycosylation of VSV glycoprotein is similar in cystic fibrosis, heterozygous carrier, and normal human fibroblasts

The single envelope glycoprotein of vesicular stomatitis virus was used as a specific probe of glycosyltransferase activities in fibroblasts from two cystic fibrosis patients, an obligate heterozygous carrier and a normal individual. Gel filtration of pronase-digested glycopeptides from both purified virions and infected cell-associated VSV glycoprotein which had been labeled with[3H] glucosamine did not reveal any significant differences in the glycosylation patterns between the different cell cultures. All 4 cell lines were apparently able to synthesize the mannose- and glucosamine- containing core structure and branch chains terminating in sialic acid which are characteristic of asparagine-linked carbohydrate side chains in cellular glycoproteins. Analysis of tryptic glycopeptides by anion-exchange chromotography indicated that the same 2 major sites on the virus polypeptide were recognized and glycosylated in all 4 VSV-infected cell cultures. These studies suggest that the basic biochemical defect(s) in cystic fibrosis is not an absence or deficiency in enzymes responsible for the biosynthesis of complex carbohydrate side chains.

Glycoprotein synthesis in gastric epithelial cells of the rat. Properties of microsomal glycoprotein glycosyltransferases

1. Optimal assay conditions were determined for a microsomal glycoprotein galactosyl- and fucosyltransferase derived from gastric epithelial scrapings with both exogenous and endogenous acceptor glycoprotein. 2. Subcellular fractionation of the homogenate yielded microsomal fractions enriched in glycosyltransferases. 3. The effect of feeding on galactosyltransferase activity per cell was examined. 4. Endogenous acceptor molecules were identified as glycoproteins after labeling by means of UDP-[3H]galactose in the cell-free system.