title: Autocatalytic formation of a covalent link between tryptophan 41 and the heme in ascorbate peroxidase.
abstract: Electronic spectroscopy, HPLC analyses, and mass spectrometry (MALDI-TOF and MS/MS) have been used to show that a covalent link from the heme to the distal Trp41 can occur on exposure of ascorbate peroxidase (APX) to H2O2 under noncatalytic conditions. Parallel analyses with the W41A variant and with APX reconstituted with deuteroheme clearly indicate that the covalent link does not form in the absence of either Trp41 or the heme vinyl groups. The presence of substrate also precludes formation of the link. Formation of a protein radical at Trp41 is implicated, in a reaction mechanism that is analogous to that proposed [Ghiladi, R. A., et al. (2005) Biochemistry 44, 15093-15105] for formation of a covalent Trp-Tyr-Met link in the closely related catalase peroxidase (KatG) enzymes. Collectively, the data suggest that radical formation at the distal tryptophan position is not an exclusive feature of the KatG enzymes and may be used more widely across other members of the class I heme peroxidase family.
authors.affiliation: Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, England.
authors.forename: Zoi
authors.initials: Z
authors.lastname: Pipirou
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Bottrill
authors.forename: Clive M
authors.initials: CM
authors.lastname: Metcalfe
authors.forename: Sharad C
authors.initials: SC
authors.lastname: Mistry
authors.forename: Sandip K
authors.initials: SK
authors.lastname: Badyal
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Rawlings
authors.forename: Emma Lloyd
authors.initials: EL
authors.lastname: Raven
mesh_terms: D060387:Ascorbate Peroxidases; D001426:Bacterial Proteins / Q000737:chemistry; D002374:Catalase / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003578:Cytochrome-c Peroxidase / Q000737:chemistry; D003905:Deuteroporphyrins / Q000378:metabolism; D006418:Heme / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000378:metabolism; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013025:Glycine max / Q000201:enzymology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013057:Spectrum Analysis; D053719:Tandem Mass Spectrometry; D014364:Tryptophan / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003905:Deuteroporphyrins; D011994:Recombinant Proteins; D006418:Heme; C028839:deuteroporphyrin-IX; D014364:Tryptophan; D006861:Hydrogen Peroxide; D010544:Peroxidases; D060387:Ascorbate Peroxidases; D003578:Cytochrome-c Peroxidase; D002374:Catalase; C480353:katG protein, Mycobacterium tuberculosis