Rate of intramolecular reduction of oxyferryl iron in horse heart myoglobin

Journal Article · Wed Apr 06 00:00:00 EDT 1994 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00086a075· OSTI ID:7162929

Fenwick, C; Marmor, S; Govindaraju, K; English, A M ^[1]; Wishart, J F; Sun, J ^[2]

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1. Concordia Univ., Montreal, Quebec (Canada)
2. Brookhaven National Lab., Upton, NY (United States)

Like heme peroxidases and other heme enzymes, myoglobin forms oxyferryl (Fe[sup IV][triple bond]O) on reaction with peroxides. We have recently observed slow intramolecular electron transfer (ET) to the oxyferryl heme of cytochrome c peroxidase (CCP) from a[sub 5]Ru[sup II] (a[sub 5]Ru = pentaammineruthenium) bound at His60 and proposed a large reorganizational energy ([lambda]) for oxyferryl heme. An obvious test of this large postulated [lambda] is to directly compare intramolecular ET rates between oxyferryl and a[sub 5]Ru centers in myoglobin with the corresponding rates in zinc-substituted sperm whale (SWMb) and recombinant human myoglobins (RHMb). Since the oxyferryl heme of horse heart myoglobin (HHMb) is significantly more stable than that of SWMb, the former protein was chosen for this study. A a[sub 5]Ru group was attached to the surface His48 of HHMb, and rates of ET over the 12.7-angstrom distance between the a[sub 5]Ru center and the ferric and oxyferryl hemes were measured by pulse radiolysis at Brookhaven National Laboratory. HHMb (0.5-10 [mu]M) solutions were prepared in N[sub 2]O-saturated sodium phosphate buffer at pH 7.0 (40 mM) containing 12 mM HCOONa to generate CO[sub 2][sup .[minus]] radicals via reaction with OH[sup .]. The bimolecular rate constant for the reduction of native HHMb(Fe[sup III]-OH[sub 2]) by CO[sub 2][sup .[minus]] was determined to be 2 x 10[sup 8] M[sup [minus]1] s[sup [minus]1] by monitoring the appearance of HHMb(Fe[sup II]) at 434 nm. 22 refs., 1 fig.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 7162929
• Journal Information: Journal of the American Chemical Society; (United States), Vol. 116:7; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
IRON COMPOUNDS
REDUCTION
CHEMICAL REACTION KINETICS
MYOGLOBIN
RADICALS
RUTHENIUM COMPLEXES
ZINC COMPOUNDS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COMPLEXES
GLOBINS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
KINETICS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PORPHYRINS
PROTEINS
REACTION KINETICS
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
550200* - Biochemistry
400201 - Chemical & Physicochemical Properties