Normal amino acid uptake by cultured human fibroblasts does not require gamma-glutamyl transpeptidase.
The uptake kinetics for four amino acids (cystine, glutamine, methionine, and alanine) which are among the best gamma-glutamyl acceptors have been determined for normal human fibroblasts and for a cell line containing undetectable quantities (< 0.5% normal mean) of gamma-glutamyl transpeptidase activity. Apparent Km and V(max) for uptake for each of the four amino acids were normal in the mutant fibroblasts. Insulin increased the uptake of alpha-aminoisobutyrate as in control cells. levels of 16 amino acids were also normal in this cell strain; the intracellular concentrations of phenylalanine, cystine, and cysteine were increased. In human fibroblasts, amino acid transport appears to proceed normally in the absence of active gamma-glutamyl transpeptidase.
Pellefigue
F
F
Section on Human Biochemical and Developmental Genetics, National Institutes of Health, Bethesda, Maryland 20014, USA.
Butler
J D
JD
Spielberg
S P
SP
Hollenberg
M D
MD
Goodman
S I
SI
Schulman
J D
JD
D000596:Amino Acids / Q000378:metabolism*; D002460:Cell Line; D005347:Fibroblasts; D006801:Humans; D007700:Kinetics; D005723:gamma-Glutamyltransferase / Q000172:deficiency / Q000378:metabolism*
D000596:Amino Acids; D005723:gamma-Glutamyltransferase