title: 4-methylthio 2-oxobutanoate transaminase: a specific target for antiproliferative agents.
abstract: We have previously shown that the addition of 4-methylthio-2-oxobutanoate (MTOB) to cultures of methionine dependent neoplastic cells which lack endogenous MTOB restores their capacity to grow in the absence of exogenous methionine. Transition state inhibitors of the MTOB transaminase,responsible for the transamination of MTOB to methionine, had also been designed and selected for their capacity to inhibit the proliferation of methionine dependent neoplastic cells but not that of normal cells in culture. We now show that the transition state analogue : L-methionine ethyl esterpyridoxal(MEEP) with a structure corresponding to the oxo acid receptor covalently linked to pyridoxamine and the amine donor analogue: D-aspartate beta hydroxamate (D-AH) are efficient inhibitors of MTOB transaminase. [3H] MEEP uptake into transformed HeLa cells is similar to that in normal MRC5 cells, yet growth inhibition is seem in the transformed but not in the normal cells.MEEP irreversibly inhibits the activity of this enzyme when added to HeLa cells in culture but not that of the purified rat liver enzyme, probably due to pyridoxal phosphate already bound in the active site. On the contrary, D-AH is a noncompetitive reversible inhibitor of the purified rat liver enzyme in vitro and also inhibits intracellular HeLa MTOB transaminase. Furthermore, in HeLa cells both inhibitors induce DNA strand breaks typical of apoptotic cell death. These results provide evidence that MTOB transaminase is a potential target for antiproliferative agents which could selectively affect methionine-dependent neoplastic cells. The transition state intermediale : MEEP as an amine acceptor analogue was found to be 20 fold more effective than D-AH as the amine donor analogue in inducing apoptosis.
authors.affiliation: Laboratorie d'Immunochimie, Faculté Médecine Lyon Sud, 69921 Oullins Cedex, France.
authors.forename: Gerard
authors.initials: G
authors.lastname: Quash
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Roch
authors.forename: Carole
authors.initials: C
authors.lastname: Charlot
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Chantepie
authors.forename: Vincent
authors.initials: V
authors.lastname: Thomas
authors.forename: Farid
authors.initials: F
authors.lastname: Hamedi-Sangsari
authors.forename: Jorge
authors.initials: J
authors.lastname: Vila
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000235:genetics; D001216:Asparagine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D003605:D-Amino-Acid Oxidase / Q000032:analysis / Q000378:metabolism; D053938:DNA Fragmentation; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D006367:HeLa Cells / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D008099:Liver / Q000201:enzymology; D008715:Methionine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology*; D011730:Pyridoxal / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*; D011733:Pyridoxamine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D051381:Rats; D000637:Transaminases / Q000032:analysis / Q000037:antagonists & inhibitors*
chemical_list: D000970:Antineoplastic Agents; C493752:L-methionine ethyl ester-pyridoxal; D005973:Glutamine; C024848:beta-aspartylhydroxamic acid; D011730:Pyridoxal; C014632:2-keto-4-methylthiobutyric acid; D011733:Pyridoxamine; D001216:Asparagine; D008715:Methionine; C038344:methionine methyl ester; D003605:D-Amino-Acid Oxidase; C493751:4-methylthio 2-oxobutanoate transaminase, human; D000637:Transaminases; C010627:pyridoxamine phosphate