An extended X-ray absorption fine structure investigation of the structure of the active site of lactoperoxidase.
Native lactoperoxidase, compound III, and the reduced forms (at pH 6 and 9) were studied using X-ray absorption spectroscopy (XAS). Native lactoperoxidase has four pyrrole nitrogen ligands at an average distance of 2.04 +/- 0.01 A, a proximal ligand at 1.91 +/- 0.02 A, and a sixth (distal) ligand at 2.16 +/- 0.03 A. Lactoperoxidase native enzyme has a first coordination shell structure that is similar to that of native lignin peroxidase [Sinclair, R., Yamazaki, I., Bumpus, J., Brock, B., Chang, C.-S., Albo, A., & Powers, L. (1992) Biochemistry 31, 4892-4900] and different from that of horseradish peroxidase [Chance, B., Powers, L., Ching, Y., Poulos, T., Schonbaum, G., Yamazaki, I., & Paul, K. (1984) Arch. Biochem. Biophys. 235, 596-611]. Similarly, lactoperoxidase compound III resembles lignin peroxidase compound III. The five-coordinated ferrous form was stable at pH 9, but at pH 6 it was rapidly converted to the six-coordinated form with a distal ligand at 2.18 +/- 0.03 A. No evidence typical of changes in spin state was obtained at the different pH values.
Chang
C S
CS
National Center for the Design of Molecular Function, Utah State University, Logan 84322-4630.
Sinclair
R
R
Khalid
S
S
Yamazaki
I
I
Nakamura
S
S
Powers
L
L
D015502:Absorptiometry, Photon; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D005260:Female; D006735:Horseradish Peroxidase / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007784:Lactoperoxidase / Q000737:chemistry*; D008024:Ligands; D008892:Milk / Q000201:enzymology; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry; D011487:Protein Conformation
D008024:Ligands; D006735:Horseradish Peroxidase; D007784:Lactoperoxidase; D010544:Peroxidases; C042858:lignin peroxidase