Mechanistic characterization of Toxoplasma gondii thymidylate synthase (TS-DHFR)-dihydrofolate reductase. Evidence for a TS intermediate and TS half-sites reactivity |
| |
Authors: | Johnson Eric F Hinz Wolfgang Atreya Chloe E Maley Frank Anderson Karen S |
| |
Institution: | Department of Pharmacology, School of Medicine, Yale University, New Haven, Connecticut 06520, USA. |
| |
Abstract: | This study describes the use of rapid transient kinetic methods to characterize the bifunctional thymidylate synthase-dihydrofolate reductase (TS-DHFR) enzyme from Toxoplasma gondii. In addition to elucidating the detailed kinetic scheme for this enzyme, this work provides the first direct kinetic evidence for the formation of a TS intermediate and for half-sites TS reactivity in human and Escherichia coli monofunctional TS and in T. gondii and Leishmania major bifunctional TS-DHFR. Comparison of the T. gondii TS-DHFR catalytic mechanism to that of the L. major enzyme reveals the mechanistic differences to be predominantly in DHFR activity. Specifically, TS ligand induced domain-domain communication involving DHFR activation is observed only in the L. major enzyme and, whereas both DHFR activities involve a rate-limiting conformational change, the change occurs at different positions along the kinetic pathway. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|