title: Efficient catalytic promiscuity in an enzyme superfamily: an arylsulfatase shows a rate acceleration of 10(13) for phosphate monoester hydrolysis.
abstract: We report a second catalytic activity of Pseudomonas aeruginosa arylsulfatase (PAS). Besides hydrolyzing sulfate monoesters, this enzyme catalyzes the hydrolysis of phosphate monoesters with multiple turnovers (>90), a k(cat) value of 0.023 s(-1), a K(M) value of 29 microM, and a kcat/K(M) ratio of 790 M(-1) s(-1) at pH 8.0. This corresponds to a remarkably high rate acceleration of 10(13) relative to the nonenzymatic hydrolysis [(k(cat)/K(M))/k(w)] and a transition-state binding constant (K(tx)) of 3.4 pM. Promiscuous phosphatase and original sulfatase activities only differ by a factor of 620 (measured by k(cat)), so the enzyme provides high accelerations for both reactions. The magnitudes and relative similarity of the kinetic parameters suggest that a functional switch from sulfatase to phosphatase activities is feasible, either by gene duplication or by direct evolution via an intermediate enzyme with dual specificity.
authors: Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom.
authors: Luis F
authors: LF
authors: Olguin
authors: Sarah E
authors: SE
authors: Askew
authors: Annmarie C
authors: AC
authors: O'Donoghue
authors: Florian
authors: F
authors: Hollfelder
mesh_terms: D001192:Arylsulfatases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055162:Biocatalysis; D020134:Catalytic Domain; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D009154:Mutation; D010755:Organophosphates / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D010755:Organophosphates; D001192:Arylsulfatases