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Cell-surface glycosyltransferases in cultured fibroblasts: increased activity and release during serum stimulation of growth.

Authors
  • LaMont, J T
  • Gammon, M T
  • Isselbacher, K J
Type
Published Article
Journal
Proceedings of the National Academy of Sciences of the United States of America
Publication Date
Mar 01, 1977
Volume
74
Issue
3
Pages
1086–1090
Identifiers
PMID: 191828
Source
Medline
License
Unknown

Abstract

Cell-surface galactosyltransferase was studied in suspensions of intact baby hamster kidney fibroblasts with both endogenous and exogenous glycoprotein acceptors. The cell-surface location of galactosyltransferase was demonstrated in experiments with the enzyme modifier alpha-lactalbumin, which does not enter the cell. The addition of alpha-lactalbumin to the assay medium for galactosyltransferase resulted in accumulation of lactose in the medium but not in the cells. There was no detectable hydrolysis of UDP-galactose to free galactose by these cells, nor did a 100-fold molar excess of free galactose inhibit cell-surface galactosyltransferase. There was a marked increase in specific activity of cell-surface exogenous galactosyltransferase in serum-stimulated as compared to resting fibroblasts. Dividing but not resting fibroblasts released galactosyltransferase, but not sialyl- or fucosyltransferase, in soluble form into the tissue culture medium. The release of galactosyltransferase was greater from virally transformed than from nontransformed fibroblasts.

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