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Crystal structure of the ascorbate peroxidase-salicylhydroxamic acid complex
Katherine H Sharp1, Peter C E Moody, Katherine A Brown
1Department of Chemistry, University of Leicester, UK.
Biochemistry
|July 9, 2004
Summary
This study reveals the aromatic binding site of ascorbate peroxidase (APX) using X-ray crystallography. The salicylhydroxamic acid (SHA) molecule binds near the heme, completing the structural understanding of APX substrate binding.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Ascorbate peroxidase (APX) is a key enzyme in plant antioxidant defense, catalyzing H(2)O(2)-dependent oxidation.
- Previous research identified the ascorbate binding site near the gamma-heme edge.
Purpose of the Study:
- To determine the X-ray crystal structure of recombinant soybean cytosolic ascorbate peroxidase (rsAPX) in complex with salicylhydroxamic acid (SHA).
- To elucidate the location of the aromatic substrate binding site in APX.
Main Methods:
- X-ray crystallography was used to determine the structure of rsAPX-SHA complex to 1.46 Å resolution.
Main Results:
- The salicylhydroxamic acid (SHA) molecule was observed to bind in a cavity near the delta-heme edge.
- Specific hydrogen bonds were identified between SHA and protein residues (Pro132, Arg38, Trp41).
- This structure provides the first direct visualization of the aromatic binding site in APX.
Conclusions:
- The determined structure completes the understanding of substrate binding properties for ascorbate peroxidase.
- The findings offer insights into the mechanism by which APX catalyzes the oxidation of diverse substrates at distinct binding locations.