title: Characterization of Aphanizomenon ovalisporum amidinotransferase involved in cylindrospermopsin synthesis.
abstract: An increasing abundance of Aphanizomenon ovalisporum in water bodies from diverse world regions has been reported in the last few years, with the majority of the isolated strains producing the toxin cylindrospermopsin (CYN), leading to a rise in ecological and health risks. The understanding of CYN synthesis is crucial in the control of CYN production. An amidinotransferase (AMDT) seems to be the first enzyme involved in the synthesis of CYN. In this study, we have cloned and overexpressed the aoaA gene from the constitutive CYN producer A. ovalisporum UAM-MAO. The recombinant purified AoaA was characterized, confirming that it is an l-arginine:glycine AMDT. It shows an optimal activity between 32 and 37°C, at pH from 8 to 9. The activity exhibits a mixed (ping-pong/sequential) kinetic mechanism, and is inhibited by the reaction product guanidine acetate (GAA) in a noncompetitive manner. Mg(2+) stimulates AoaA activity while Co(2+) and Mn(2+) inhibit it. AoaA conserves the critical residues of the catalytic site and substrate specificity of AMDTs, as the previously reported AMDT from Cylindrospermopsis raciborskii Cyr. Both proteins can be included in a new group of prokaryotic AMDTs involved in CYN production.
authors.affiliation: Departamento de Biología, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049, Madrid, Spain.
authors.forename: Angel
authors.initials: A
authors.lastname: Barón-Sola
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Gutiérrez-Villanueva
authors.forename: Francisca F
authors.initials: FF
authors.lastname: Del Campo
authors.forename: Soledad
authors.initials: S
authors.lastname: Sanz-Alférez
mesh_terms: D000470:Alkaloids; D000579:Amidinotransferases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D046890:Aphanizomenon / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D001427:Bacterial Toxins; D003001:Cloning, Molecular; D016000:Cluster Analysis; D017124:Conserved Sequence; D000087522:Cyanobacteria Toxins; D020536:Enzyme Activators / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism; D004795:Enzyme Stability; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008670:Metals / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D014498:Uracil / Q000031:analogs & derivatives* / Q000096:biosynthesis
chemical_list: D000470:Alkaloids; D001427:Bacterial Toxins; D000087522:Cyanobacteria Toxins; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D008670:Metals; D011994:Recombinant Proteins; C089595:cylindrospermopsin; D014498:Uracil; D000579:Amidinotransferases