title: Discovery of a cytokinin deaminase.
abstract: An enzyme of unknown function within the amidohydrolase superfamily was discovered to catalyze the hydrolysis of N-6-substituted adenine derivatives, several of which are cytokinins. Cytokinins are a common type of plant hormone and N-6-substituted adenines are also found as modifications to tRNA. Patl2390, from Pseudoalteromonas atlantica T6c, was shown to hydrolytically deaminate N-6-isopentenyladenine to hypoxanthine and isopentenylamine with a k(cat)/K(m) of 1.2 × 10(7) M(-1) s(-1). Additional substrates include N-6-benzyl adenine, cis- and trans-zeatin, kinetin, O-6-methylguanine, N-6-butyladenine, N-6-methyladenine, N,N-dimethyladenine, 6-methoxypurine, 6-chloropurine, and 6-thiomethylpurine. This enzyme does not catalyze the deamination of adenine or adenosine. A comparative model of Patl2390 was computed using the three-dimensional crystal structure of Pa0148 (PDB code  3PAO ) as a structural template, and docking was used to refine the model to accommodate experimentally identified substrates. This is the first identification of an enzyme that will hydrolyze an N-6-substituted side chain larger than methylamine from adenine.
authors.forename: Alissa M
authors.initials: AM
authors.lastname: Goble
authors.forename: Hao
authors.initials: H
authors.lastname: Fan
authors.forename: Andrej
authors.initials: A
authors.lastname: Sali
authors.forename: Frank M
authors.initials: FM
authors.lastname: Raushel
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000378:metabolism; D000619:Aminohydrolases / Q000737:chemistry / Q000378:metabolism*; D003583:Cytokinins / Q000378:metabolism*; D003641:Deamination; D008958:Models, Molecular; D011549:Pseudomonas / Q000737:chemistry / Q000201:enzymology*; D011550:Pseudomonas aeruginosa / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D003583:Cytokinins; D000619:Aminohydrolases; D000225:Adenine