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Glutamyl hydrolase. pharmacological role and enzymatic characterization.
Human gamma-glutamyl hydrolase: cloning and characterization of the enzyme expressed in vitro.
- R. Yao, E. Schneider, T. Ryan, J. Galivan
- BiologyProceedings of the National Academy of Sciences…
- 17 September 1996
A cDNA encoding human gamma-glutamyl hydrolase has been identified by searching an expressed sequence tag data base and using rat Gamma-glUTamyl Hydrolase cDNA as the query sequence, showing 67% identity to that of rat gamma- glutamy hydrol enzyme.
Biochemical studies on PT523, a potent nonpolyglutamatable antifolate, in cultured cells.
Inhibition of H35 cell growth by PT523 was associated with a concentration- and time-related decrease in de novo dTMP and purine biosynthesis, suggesting that penetration of the cell probably involves, at least in part, active transport by the MTX/reduced folate carrier.
Evidence for the cytotoxic activity of polyglutamate derivatives of methotrexate.
- J. Galivan
- Chemistry, BiologyMolecular pharmacology
Protection studies demonstrated that both thymidine and hypoxanthine are needed to prevent methotrexate toxicity, offering evidence that inhibition of cell growth is due to a depletion of reduced folate coenzymes, and results demonstrate that the polyglutamates have at least an equivalent affinity for the enzyme in the intact cell when compared to metotrexate.
Acquisition of resistance to antifolates caused by enhanced gamma-glutamyl hydrolase activity.
Evidence for the involvement of gamma-glutamyl hydrolase in resistance is derived from the observation that polyglutamate derivatives of 10-propargyl-5,8-dideazafolate in resistant cells are maintained at one-third the amount of that in parental cells in the presence of the same extracellular concentration.
Secretion of gamma-glutamyl hydrolase in vitro.
Altering in the cellular and secreted H35 cell gamma-glutamyl hydrolase levels in response to changes in culture conditions revealed that glutamine enhances activity while insulin diminishes it, which suggests that both act primarily as endopeptidases.
Methotrexate metabolism analysis in blood and liver of rheumatoid arthritis patients. Association with hepatic folate deficiency and formation of polyglutamates.
Serum and red blood cell methotrexate (MTX) levels, as well as hepatic levels of MTX and folate, were analyzed in patients who had received long-term oral MTX weekly for the treatment of rheumatoid arthritis, and it is possible that MTX hepatotoxicity is related to reduced hepatic folate levels and formation ofMTX polyglutamates.
Transport and metabolism of methotrexate in normal and resistant cultured rat hepatoma cells.
- J. Galivan
- Biology, ChemistryCancer research
- 1 March 1979
The results suggest that the cells become resistant as a result of a stable change in the transport system for MTX, but the mechanism of this process is not yet understood.
Efflux of methotrexate and its polyglutamate derivatives from hepatic cells in vitro.
It is demonstrated that intact methotrexate polyglutamates can leave the cells, but this is probably not as rapid in H35 cells as cleavage to methotreysate and subsequent efflux, and that metHotrexate does so much more rapidly, resulting in selective retention of methot Rexate polyGLutamate derivatives.