Structural implication of the heme-linked ionization of horseradish peroxidase probed by the Fe-histidine stretching Raman line.

Heme Structural Perturbation of PEG-Modified Horseradish Peroxidase C in Aromatic Organic Solvents Probed by Optical Absorption and Resonance Raman Dispersion Spectroscopy

“…The structure of dehydrated HRP-PEG dissolved in organic solvents essentially resembles the structure of native HRP in water (Ryu and Dordick, 1992;Kamiya et al, 2000;Al-Azzam et al, 2002). Despite the striking similarities in structure and enzymatic activity, however, special properties have been reported for HRP in some aromatic organic media, such as BHA (Teraoka and Kitagawa, 1981) and benzene (Mabrouk and Spiro, 1998). Akasaka et al (1995) showed that HRP efficiently catalyzes the hydroxylation of benzene in the presence of H 2 O 2 , similar to what was obtained for cytochrome P450.…”

“…Table 1). In earlier work, this observation has been interpreted as reflecting an hc-hs state (Smulevich et al, 1991(Smulevich et al, , 1994Teraoka and Kitagawa, 1981). This, however, is somewhat at odds with the crystal structure of HRPc:BHA (Henriksen et al, 1998), which exhibits a wateriron distance of 2.7 Å .…”

“…In the spectra of native HRP, n 3 contains at least two components at 1492 and 1500 cm ÿ1 , which represent coexisting protein conformations with their iron atoms exhibiting pentacoordinate high spin (pc-hs) and pentacoordinate quantum mixed spin (pc-qms) states, respectively (Feis et al, 1998;Howes et al, 2000Howes et al, , 2001. The weaker band at 1492 cm ÿ1 was previously assigned to a hexacoordinate high spin (hc-hs) (Rakshit and Spiro, 1974;Teraoka and Kitagawa, 1981;Evangelista-Kirkup et al, 1985;Palanappian and Terner, 1989.;Smulevich et al, 1991) and has recently been reassigned as pentacoordinated high spin state (Feis et al, 1998. We also assign it to pc-hs because this is consistent with the observation of a n 10 band at 1629 cm ÿ1 , which is diagnostic of a pc-hs state for HRP (Smulevich et al, 1991, Howes et al, 2001 and also for barley (Howes et al, 1999) and soybean seed coat peroxidases (Nissum et al, 1998).…”

“…Since resonance Raman spectra of Teraoka and Kitagawa (1981) reveal no changes of the 379 cm ÿ1 Raman line of the propionate substituent, any interaction of BHA with the respective pyrrole groups are likely to be weak. The crystal structure (Henriksen et al, 1998) exhibits BHA nearly parallel oriented to the heme group and in van der Waals contact with a C m atom of one of the methine bridges between the two pyrrole groups with methyl and vinyl substituents.…”

Understanding molecular enzymology of porphyrin-binding α + β barrel proteins - One fold, multiple functions

“…The ν (Fe-His) stretching band exhibits a wavenumber between 205 and 250 cm −1 . When the proximal histidine is strongly interacting with other residues, the imidazolate character increases and the ν (Fe-His) stretching band is between 240 and 250 cm −1 [ 87 ]. A weak imidazolate character, on the other hand, is characterized by frequencies of 205 to 215 cm −1 .…”