title: Structure of milk lactoperoxidase. A study using circular dichroism and difference absorption spectroscopy.
abstract: Circular dichroism spectra of milk lactoperoxidase, its fluoride and cyanide derivatives, and those of ferrous lactoperoxidase and its carbonyl and cyanide compounds, were recorded in the wavelength region 200-670 nm. All derivatives have split ellipticity bands, suggesting that lactoperoxidase has a narrow heme pocket that prevents ligands forming linear iron-ligand bonds. Difference absorption spectroscopy of the enzyme in the far-ultraviolet region supports the previously held view that the fifth ligand of the heme iron is histidine. The secondary structure of lactoperoxidase, calculated from the far-ultraviolet circular dichroism spectrum, contains 65% beta-structure, 23% alpha-helix and 12% unordered structure. Reduction of lactoperoxidase with dithionite gives two forms, indicating that after reduction some compound arising from dithionite binds in the vicinity of the heme iron.
mesh_terms: D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002942:Circular Dichroism; D005260:Female; D007784:Lactoperoxidase; D008892:Milk / Q000201:enzymology*; D010544:Peroxidases; D013056:Spectrophotometry, Ultraviolet; D013057:Spectrum Analysis
chemical_list: D007784:Lactoperoxidase; D010544:Peroxidases