title: Design, synthesis and evaluation of transition-state analogue inhibitors of Escherichia coli gamma-glutamylcysteine synthetase.
abstract: Phosphinic acid-, sulfoximine- and sulfone-based transition-state analogues were synthesized and evaluated as inhibitors of Escherichia coli gamma-glutamylcysteine synthetase. These compounds have a carboxyl function at the beta-carbon to the tetrahedral central hetero atom so as to mimic the carboxyl group of the attacking cysteine in the transition state. The phosphinic acid- and the sulfoximine-based compounds were found to be potent ATP-dependent inactivators, both showing a slow-binding kinetics with overall affinities and second-order inactivation rates of one to two orders of magnitude greater than those of L-buthionine (SR)-sulfoximine (L-BSO). The sulfone was a simple reversible inhibitor without causing ATP-dependent enzyme inactivation, but its affinity toward the enzyme was still five times greater than that of L-BSO, indicating that the beta-carboxyl function plays a key role in the recognition of the inhibitors by the enzyme. The sulfoximine with (S)-beta-carbon to the sulfur was synthesized stereoselectively, and the two diastereomers with respect to the chiral sulfur atom were separated as a cyclic sulfoximine derivative. The sulfoximine with R-configuration around the sulfur served as an extremely powerful ATP-dependent inactivator with an overall inhibition constant of 39 nM and an inactivation rate of 6750 M-1 s-1, which correspond to 1260-fold higher affinity and almost 1400-fold greater inactivation rate as compared with L-BSO. The sulfoximine with (S)-sulfur was a simple reversible inhibitor with an inhibition potency comparable to that of the sulfone. The synthesis and inhibition profile of the N-phosphoryl sulfoximine is also described.
authors.affiliation: Institute for Chemical Research, Kyoto University, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Tokutake
authors.forename: J
authors.initials: J
authors.lastname: Hiratake
authors.forename: M
authors.initials: M
authors.lastname: Katoh
authors.forename: T
authors.initials: T
authors.lastname: Irie
authors.forename: H
authors.initials: H
authors.lastname: Kato
authors.forename: J
authors.initials: J
authors.lastname: Oda
mesh_terms: D002087:Butyrates / Q000138:chemical synthesis* / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000494:pharmacology*; D004926:Escherichia coli / Q000201:enzymology*; D005721:Glutamate-Cysteine Ligase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D063065:Organophosphonates / Q000138:chemical synthesis; D009943:Organophosphorus Compounds / Q000138:chemical synthesis* / Q000494:pharmacology*
chemical_list: C116530:2-amino(4-(2-carboxybutyl)sulfonyl)butanoic acid; C116531:2-amino-4-(2-carboxybutyl-(N-phosphoryl)sulfonimidoyl)butanoic acid; C116529:2-amino-4-(2-carboxybutylsulfonimidoyl)butanoic acid; D002087:Butyrates; D004791:Enzyme Inhibitors; D063065:Organophosphonates; D009943:Organophosphorus Compounds; D005721:Glutamate-Cysteine Ligase