Biochemistry 2010, 49, 8857–8872 8857 DOI: 10.1021/bi100499a
Unprecedented Peroxidase-like Activity of Rhodnius prolixus Nitrophorin 2: Identification of the [FeIVdO Por•]þ and [FeIVdO Por](Tyr38•) Intermediates and Their Role(s) in Substrate Oxidation† Rahul Singh,‡ Robert E. Berry,§ Fei Yang,§ Hongjun Zhang,§ F. Ann Walker,*,§ and Anabella Ivancich*,‡ ‡
CNRS URA 2096. CEA, iBiTec-S, Laboratoire des Hyperfr equences, M etalloprot eines et Syst emes de Spin, F-91191 Gif-sur-Yvette, France, and §Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721-0041 Received April 2, 2010; Revised Manuscript Received August 18, 2010 ABSTRACT: We have identified a novel enzymatic reaction for nitrophorin 2 (NP2), a heme protein previously characterized as a nitric oxide carrier in the saliva of the Rhodnius prolixus insect. NP2 exhibited levels of peroxidase activity comparable to those of the bifunctional peroxidases (KatGs), despite their heme pocket structural differences (heme ruffling, Tyr38 and Tyr85 in hydrogen bonding interactions with the propionates in NP2). The intermediates of the peroxidase-like reaction of NP2 were identified by Electron Paramagnetic Resonance (EPR) and electronic absorption spectroscopies. The EPR spectrum consistent with an [FeIVdO Por•]þ species was detected at pH
