PDBsum entry 2wd4

Oxidoreductase

PDB id: 2wd4

Contents

Protein chain

248 a.a. *

Ligands

SO4 ×2

TBV

Metals

_FE

_NA

Waters ×189

* Residue conservation analysis

PDB id:

2wd4

Name:

Oxidoreductase

Title:

Ascorbate peroxidase as a heme oxygenase: w41a variant product with t- butyl peroxide

Structure:

Ascorbate peroxidase. Chain: a. Fragment: residues 2-250. Synonym: cytosolic ascorbate peroxidase 1. Engineered: yes. Mutation: yes. Other_details: reaction product with t-butyl peroxide showing heme oxygenase activity form biliverdin derivative

Source:

Glycine max. Soybean. Organism_taxid: 3847. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.40Å R-factor: 0.191 R-free: 0.216

Authors:

S.K.Badyal,C.L.Metcalfe,A.Gumiero,E.L.Raven,P.C.E.Moody

Key ref:

S.K.Badyal et al. (2009). Evidence for heme oxygenase activity in a heme peroxidase. Biochemistry, 48, 4738-4746. PubMed id: 19309109

Date:

19-Mar-09 Release date: 07-Apr-09

Protein chain

Q43758  (Q43758_SOYBN) -  L-ascorbate peroxidase from Glycine max

Seq: 250 a.a.

Struc: 248 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.1.11.1.11 - L-ascorbate peroxidase.
• Reaction: L-ascorbate + H2O2 = L-dehydroascorbate + 2 H2O
• Cofactor: Heme

Heme (Bound ligand (Het Group name = TBV) matches with 83.67% similarity)

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

Biochemistry 48:4738-4746 (2009)

PubMed id: 19309109

Evidence for heme oxygenase activity in a heme peroxidase.

S.K.Badyal, G.Eaton, S.Mistry, Z.Pipirou, J.Basran, C.L.Metcalfe, A.Gumiero, S.Handa, P.C.Moody, E.L.Raven.

ABSTRACT

The heme peroxidase and heme oxygenase enzymes share a common heme prosthetic group but catalyze fundamentally different reactions, the first being H(2)O(2)-dependent oxidation of substrate using an oxidized Compound I intermediate, and the second O(2)-dependent degradation of heme. It has been proposed that these enzymes utilize a common reaction intermediate, a ferric hydroperoxide species, that sits at a crossroads in the mechanism and beyond which there are two mutually exclusive mechanistic pathways. Here, we present evidence to support this proposal in a heme peroxidase. Hence, we describe kinetic data for a variant of ascorbate peroxidase (W41A) which reacts slowly with tert-butyl hydroperoxide and does not form the usual peroxidase Compound I intermediate; instead, structural data show that a product is formed in which the heme has been cleaved at the alpha-meso position, analogous to the heme oxygenase mechanism. We interpret this to mean that the Compound I (peroxidase) pathway is shut down, so that instead the reaction intermediate diverts through the alternative (heme oxygenase) route. A mechanism for formation of the product is proposed and discussed in the light of what is known about the heme oxygenase reaction mechanism.