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|3ret, resolution 1.79Å ()|
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|Gene:||PA4230, pchB (Pseudomonas aeruginosa)|
Salicylate and Pyruvate Bound Structure of the Isochorismate-Pyruvate Lyase K42E Mutant from Pseudomonas aerugionsa
An isochorismate-pyruvate lyase with adventitious chorismate mutase activity from Pseudomonas aerugionsa (PchB) achieves catalysis of both pericyclic reactions in part by the stabilization of reactive conformations and in part by electrostatic transition-state stabilization. When the active site loop Lys42 is mutated to histidine, the enzyme develops a pH dependence corresponding to a loss of catalytic power upon deprotonation of the histidine. Structural data indicate that the change is not due to changes in active site architecture, but due to the difference in charge at this key site. With loss of the positive charge on the K42H side chain at high pH, the enzyme retains lyase activity at approximately 100-fold lowered catalytic efficiency but loses detectable mutase activity. We propose that both substrate organization and electrostatic transition state stabilization contribute to catalysis. However, the dominant reaction path for catalysis is dependent on reaction conditions, which influence the electrostatic properties of the enzyme active site amino acid side chains.
pH Dependence of Catalysis by Pseudomonas aeruginosa Isochorismate-Pyruvate Lyase: Implications for Transition State Stabilization and the Role of Lysine 42., Olucha J, Ouellette AN, Luo Q, Lamb AL, Biochemistry. 2011 Jul 22. PMID:21751784
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.