title: Enzymatic characterization and inhibitor discovery of a new cystathionine {gamma}-synthase from Helicobacter pylori.
abstract: Cystathionine gamma-synthase (CGS) catalyses the first step of the transsulfuration pathway that converts l-cysteine to l-homocysteine in bacteria, whereas this pathway is absent in human. In this report, we identified a new metB gene from Helicobacter pylori strain SS1, and the recombinant H. pylori Cystathionine gamma-synthase (HpCGS) was successfully cloned, expressed and purified in Escherichia coli system. Enzymatic study of HpCGS indicated that the K(m) and k(cat)/K(m) values against the substrate O-succinyl-l-homoserine (l-OSHS) were 3.02 mM and 98.7 M(-)(1)s(-)(1), respectively. Moreover, four natural products (alpha-lapachone, 9-hydroxy-alpha-lapachone, Paulownin and Yangambin, Fig. 1) were discovered to demonstrate inhibitory activities against HpCGS with IC(50) values of 11 +/- 3, 9 +/- 1, 19 +/- 2 and 27 +/- 6 microM, respectively. All these four inhibitors prevent the binding of l-OSHS to HpCGS in a non-competitive fashion. In vitro antibacterial assays further indicated that these four discovered compounds could highly inhibit the growth of H. pylori and exhibited strong inhibitory specificity against H. pylori related to E. coli.
authors.affiliation: Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China.
authors.forename: Yunhua
authors.initials: Y
authors.lastname: Kong
authors.forename: Dalei
authors.initials: D
authors.lastname: Wu
authors.forename: Haiyun
authors.initials: H
authors.lastname: Bai
authors.forename: Cong
authors.initials: C
authors.lastname: Han
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Lili
authors.initials: L
authors.lastname: Chen
authors.forename: Lihong
authors.initials: L
authors.lastname: Hu
authors.forename: Hualiang
authors.initials: H
authors.lastname: Jiang
authors.forename: Xu
authors.initials: X
authors.lastname: Shen
mesh_terms: D000429:Alcohol Oxidoreductases / Q000302:isolation & purification; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D019757:Carbon-Oxygen Lyases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D016480:Helicobacter pylori / Q000201:enzymology*; D007700:Kinetics; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D000429:Alcohol Oxidoreductases; C047961:2-hydroxyisocaproate dehydrogenase; C022696:O-succinylhomoserine (thiol)-lyase; D019757:Carbon-Oxygen Lyases