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Crystal structure of recombinant pea cytosolic ascorbate peroxidase
1Department of Physiology and Biophysics, University of California, Irvine 92717, USA.
Biochemistry
|April 4, 1995
Summary
The crystal structure of pea cytosolic ascorbate peroxidase reveals a homodimer with a fold similar to cytochrome c peroxidase. A unique cation binding site near a key tryptophan residue may be functionally important.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Ascorbate peroxidase (APX) is a crucial enzyme in plant antioxidant systems.
- Understanding APX structure provides insights into reactive oxygen species scavenging mechanisms.
Purpose of the Study:
- To determine the high-resolution crystal structure of recombinant pea cytosolic ascorbate peroxidase.
- To compare the structural features of pea APX with other known peroxidases, particularly cytochrome c peroxidase (CCP).
Main Methods:
- X-ray crystallography was used to refine the crystal structure of pea cytosolic APX.
- The structure was refined to 2.2 A resolution with an R-factor of 0.19.
- Structural comparisons were made with cytochrome c peroxidase using root mean square differences.
Main Results:
- The refined structure revealed pea APX as a noncovalent homodimer, with each monomer containing a heme group.
- The overall fold of pea APX monomers closely resembles that of CCP, with high similarity in active site architecture.
- A novel cation binding site was identified in pea APX, located near the conserved proximal tryptophan residue (Trp179).
Conclusions:
- Pea cytosolic APX shares significant structural homology with CCP, particularly at the active site.
- The identified cation binding site represents a key structural difference and may play a functional role in APX activity.
- This structural information advances the understanding of peroxidase function and evolution.