Monoesterase activity of a purple acid phosphatase mimic with a cyclam platform.

Peter Comba, Lawrence R Gahan, Graeme R Hanson, Valeriu Mereacre, Christopher J Noble, Annie K Powell, Ion Prisecaru, Gerhard Schenk, Marta Zajaczkowski-Fischer

Index: Chemistry 18(6) , 1700-10, (2012)

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Abstract

The synthesis and characterization of a novel dinucleating ligand L (L=4,11-dimethyl-1,8-bis{2-[N-(di-2-pyridylmethyl)amino]ethyl}cyclam) and its μ-oxo-bridged diferric complex [(H(2)L){Fe(III)(2)(O)}(Cl)(4)](2+) are reported. This diiron(III) complex is the first example of a truly functional purple acid phosphatase (PAP) mimic as it accelerates the hydrolysis of the activated phosphomonoester 2,4-dinitrophenyl phosphate (DNPP). The spectroscopic and kinetic data indicate that only substrates that are monodentately bound to one of the two ferric ions can be attacked by a suitable nucleophile. This is, most probably, a terminal iron(III)-bound hydroxide. DFT calculations support this assumption and also highlight the importance of secondary interactions, exerted by the protonated cyclam platform, for the positioning and activation of the iron(III)-bound substrate. Similar effects are postulated in the native enzyme but addressed in PAP mimics for the first time.Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.