title: Purification and characterization of Helicobacter pylori arginase, RocF: unique features among the arginase superfamily.
abstract: The urea cycle enzyme arginase (EC 3.5.3.1) hydrolyzes l-arginine to l-ornithine and urea. Mammalian arginases require manganese, have a highly alkaline pH optimum and are resistant to reducing agents. The gastric human pathogen, Helicobacter pylori, also has a complete urea cycle and contains the rocF gene encoding arginase (RocF), which is involved in the pathogenesis of H. pylori infection. Its arginase is specifically involved in acid resistance and inhibits host nitric oxide production. The rocF gene was found to confer arginase activity to Escherichia coli; disruption of plasmid-borne rocF abolished arginase activity. A translationally fused His(6)-RocF was purified from E. coli under nondenaturing conditions and had catalytic activity. Remarkably, the purified enzyme had an acidic pH optimum of 6.1. Both purified arginase and arginase-containing H. pylori extracts exhibited optimal catalytic activity with cobalt as a metal cofactor; manganese and nickel were significantly less efficient in catalyzing the hydrolysis of arginine. Viable H. pylori or E. coli containing rocF had significantly more arginase activity when grown with cobalt in the culture medium than when grown with manganese or no divalent metal. His(6)-RocF arginase activity was inhibited by low concentrations of reducing agents. Antibodies raised to purified His(6)-RocF reacted with both H. pylori and E. coli extracts containing arginase, but not with extracts from rocF mutants of H. pylori or E. coli lacking the rocF gene. The results indicate that H. pylori RocF is necessary and sufficient for arginase activity and has unparalleled features among the arginase superfamily, which may reflect the unique gastric ecological niche of this organism.
authors.affiliation: Department of Microbiology & Immunology, University of South Alabama, College of Medicine, Mobile, AL 36688, USA. dmcgee@jaguar1.usouthal.edu
authors.forename: David J
authors.initials: DJ
authors.lastname: McGee
authors.forename: Jovanny
authors.initials: J
authors.lastname: Zabaleta
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Viator
authors.forename: Traci L
authors.initials: TL
authors.lastname: Testerman
authors.forename: Augusto C
authors.initials: AC
authors.lastname: Ochoa
authors.forename: George L
authors.initials: GL
authors.lastname: Mendz
mesh_terms: D001119:Arginase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001120:Arginine / Q000378:metabolism; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D015153:Blotting, Western; D003035:Cobalt / Q000737:chemistry / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D016480:Helicobacter pylori / Q000201:enzymology* / Q000235:genetics; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008345:Manganese / Q000737:chemistry / Q000378:metabolism; D008623:Mercaptoethanol / Q000494:pharmacology; D009532:Nickel / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D003035:Cobalt; D008345:Manganese; D008623:Mercaptoethanol; D009532:Nickel; D001120:Arginine; C402431:RocF protein, Helicobacter pylori; D001119:Arginase; D004229:Dithiothreitol