Photochemically Modified Myeloperoxidase, with Optical Spectral Properties Analogous to Those of Lactoperoxidase, Retains Its Original Catalytic Activity

Hiroshi Hori, Masao Ikeda-Saito

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

During the course of a reducing reaction using ketyl radicals generated from ketone photoreduction with ultraviolet light, a photoinduced chemical modification of the chromophore group in myeloperoxidase has been found. Light absorption and resonance Raman spectra for this modified enzyme indicated an iron porphyrin chromophore group. The alkaline pyridine hemochrome of the modified enzyme exhibited an optical spectrum closely related to that of iron protoporphyrin IX. The chromophore group of the modified myeloperoxidase was cleaved from the protein by methoxide. Proton magnetic resonance of the diamagnetic bis(cyanide) compound of the extracted heme group showed the presence of two vinyl and three methyl side chains associated with a porphyrin macrocycle. These data provide further insight into the structure of the active site in myeloperoxidase. The EPR spectral properties and enzymatic activities of the native myeloperoxidase are essentially conserved in the modified enzyme. Our present results indicate that the heme peripheral substituent is modified while the stereochemical structure surrounding the chromophore group is not altered by the photochemical modification.

Original languageEnglish
Pages (from-to)7106-7112
Number of pages7
JournalBiochemistry
Volume29
Issue number30
DOIs
Publication statusPublished - 1990 Jul 1

ASJC Scopus subject areas

  • Biochemistry

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