Efficient Catalytic Promiscuity in an Enzyme Superfamily: An Arylsulfatase Shows a Rate Acceleration of 1013 for Phosphate Monoester Hydrolysis

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• 作者：Luis F. Olguin ; Sarah E. Askew ; AnnMarie C. O’ ; Donoghue ; Florian Hollfelder
• 刊名：Journal of the American Chemical Society
• 出版年：2008
• 出版时间：December 10, 2008
• 年：2008
• 卷：130
• 期：49
• 页码：16547-16555
• 全文大小：299K
• 年卷期：v.130,no.49(December 10, 2008)
• ISSN：1520-5126

文摘

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 μM, and a k_cat/K_M ratio of 790 M⁻¹ s⁻¹ at pH 8.0. This corresponds to a remarkably high rate acceleration of 10¹³ 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.