Preparation and initial characterization of the compound I, II, and III states of iron methylchlorin-reconstituted horseradish peroxidase and myoglobin: Models for key intermediates in iron chlorin enzymes

To better understand the spectral properties of high valent and oxyferrous states in naturally occurring iron chlorin-containing proteins, we have pre pared the oxoferryl compound I derivative of iron methylchlorin-reconstitut ed horseradish peroxidase (MeChl-HRP) and the compound II and oxyferrous co mpound III states of iron MeChl-reconstituted myoglobin. Initial spectral c haracterization has been carried out with W-visible absorption and magnetic circular dichroism. In addition, the peroxidase activity of iron MeChl-HRP in pyrogallol oxidation has been found to be 40% of the rate for native HR P. Previous studies of oxoferryl chlorins have employed tetraphenylchlorins in organic solvents at low temperatures; stable oxyferrous chlorins have n ot been previously examined. The present study describes the compound I, II , and III states of histidine-ligated iron chlorins in a protein environmen t for the first time. (C) 2000 Academic Press.