Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.1.1.148 (Thy1)
 1,210 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The novel flavin-dependent thymidylate synthase, ThyX, is absent in humans but several pathogenic bacteria depend exclusively on ThyX activity to synthesize thymidylate. Reduction of the enzyme-bound FAD by NADPH is suggested to be the critical first step in ThyX catalysis. We soaked Mycobacterium tuberculosis ThyX-FAD-BrdUMP ternary complex crystals in a solution containing NADP+ to gain structural insights into the reductive step of the catalytic cycle. Surprisingly, the NADP+ displaced both FAD and BrdUMP from the active site. In the resultant ThyX-NADP+ binary complex, the AMP moiety is bound in a deep pocket similar to that of the same moiety of FAD in the ternary complex, while the nicotinamide part of NADP+ is engaged in a limited number of contacts with ThyX. The additional 2'-phosphate group attached to the AMP ribose of NADP+ could be accommodated with minor rearrangement of water molecules. The newly introduced 2'-phosphate groups are engaged in water-mediated interactions across the non-crystallographic 2-fold axis of the ThyX tetramer, suggesting possibilities for design of high-affinity bivalent inhibitors of this intriguing enzyme.
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PMID:NADP+ expels both the co-factor and a substrate analog from the Mycobacterium tuberculosis ThyX active site: opportunities for anti-bacterial drug design. 1673 23

Tuberculosis (TB), mainly caused by Mycobacterium tuberculosis (Mtb), is an infection that is responsible for roughly 1.5 million deaths per year. The situation is further complicated by the wide-spread resistance to the existing first- and second-line drugs. As a result of this, it is urgent to develop new drugs to combat the resistant bacteria as well as have lower side effects, which can promote adherence to the treatment regimens. Targeting the de novo synthesis of thymidylate (dTMP) is an important pathway to develop drugs for TB. Although Mtb carries genes for two families of thymidylate synthases (TS), ThyA and ThyX, only ThyX is essential for its normal growth. Both enzymes catalyze the conversion of uridylate (dUMP) to dTMP but employ a different catalytic approach and have different structures. Also, ThyA is the only TS found in humans. This is the rationale for identifying selective inhibitors against ThyX. We exploited the NADPH oxidation to NADP+ step, catalyzed by ThyX, to develop a spectrophotometric biochemical assay. Success of the assay was demonstrated by its effectiveness (average Z'=0.77) and identification of selective ThyX inhibitors. The most potent compound is a tight-binding inhibitor with an IC50 of 710nM. Its mechanism of inhibition is analyzed in relation to the latest findings of ThyX mechanism and substrate and cofactor binding order.
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PMID:Discovery of a new Mycobacterium tuberculosis thymidylate synthase X inhibitor with a unique inhibition profile. 2835 6