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Studies on the regulation of the three enzymes of the leloir pathway in cultured mammalian cells . I. Effect of substitution of galactose for glucose as the sole hexose in the medium in human diploid cell strains and in a rat hepatoma line
Author(s) -
Stern Elizabeth Sell,
Krooth Robert S.
Publication year - 1975
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1040860111
Subject(s) - galactose , hexose , enzyme , biochemistry , substitution (logic) , chemistry , biology , computer science , programming language
In human diploid cell strains, the substitution of galactose for glucose as the sole hexose in the medium had no measurable effect on the specific activity of the cell protein for any of the three enzymes of the Leloir pathway. These enzymes are galactokinase, α‐D‐galactose‐1‐phosphate:UDP glucose uridylyl transferase and UDP galactose 4‐epimerase. A cell strain from a patient with galactosemia had no detectable activity for the transferase. The substitution of galactose for glucose in the medium of these cells (which has been shown to cause the cells to accumulate galactose‐1‐phosphate) also failed to affect cellular activity for the three enzymes. Similarly, the three activities failed to respond to the substitution of galactose for glucose in cultures of a rat hepatoma line. Cells of this line have been shown by others to perform a number of the tissue‐specific functions of liver. The failure of galactose to stimulate increased cellular activity for the three enzymes represents a striking difference between the behavior of these enzymes in human diploid cell strains and their behavior in E. coli .