Resolution of the reaction sequence during the reduction of O[sub 2] by cytochrome oxidase

Journal Article · Fri Jan 01 04:00:00 EST 1993 · Proceedings of the National Academy of Sciences of the United States of America; (United States)

DOI:https://doi.org/10.1073/pnas.90.1.237· OSTI ID:6900484

Varotsis, C; Zhang, Yong; Babcock, G T ^[1]; Appelman, E H ^[2]

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1. Michigan State Univ., East Lansing (United States)
2. Argonne National Lab., IL (United States)

This paper reports on the reduction of dioxygen by the mitochondrial enzyme, cytochrome oxidase. In agreement with earlier reports, Fe[sup 2+]-O[sub 2] and Fe[sup 3+]-OH[sup [minus]] are detected in the initial and final stages of the reaction, respectively. Two additional intermediates, a peroxy [Fe[sup 3+]-O[sup [minus]]-O[sup [minus]](H)] and a ferryl (Fe[sup 4+][double bond]O), occur transiently. The peroxy species shows an oxygen-isotope-sensitive mode at 358 cm[sup [minus]1] that is assigned as the [nu](Fe[sup 3+]-O[sup [minus]]) stretching vibration. The authors kinetic analysis indicates that the peroxy species they detect occurs upon proton uptake from bulk solution; whether this species bridges to Cu[sub B] remains uncertain. For the ferryl, [nu](Fe[sup 4+][double bond]O) is at 790 cm[sup [minus]1]. In their time-resolved spectra, the 358 cm[sup [minus]1] mode appears prior to the 790 cm[sup [minus]1] vibration. Rate constants to several steps in the linear reaction sequence proposed by G.T. Babcock and M. Wikstroem [(1992) Nature (London) 356, 301-309]. Simulations of this kinetic scheme provide insight into the temporal behavior of key intermediates in the O[sub 2] reduction process. Analysis indicates the presence of a mechanism in which conditions that allow efficient dioxygen bond cleavage are not inherent to the active site but are only established as the reaction proceeds. This catalytic strategy provides an effective means by which to couple the free energy available in later intermediates in the reduction reaction to the proton-pumping function of the enzyme. 47 refs., 5 figs.

• OSTI ID: 6900484
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (United States), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (United States) Vol. 90:1; ISSN PNASA6; ISSN 0027-8424
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
CARBOXYLIC ACIDS
CATALYTIC EFFECTS
CELL CONSTITUENTS
CHEMICAL REACTIONS
CYTOCHROME OXIDASE
ELEMENTS
ENERGY
ENZYME ACTIVITY
ENZYMES
FREE ENERGY
HAEM DEHYDROGENASES
HEME
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IRON
MAMMALS
METALS
MITOCHONDRIA
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
OXYGEN
PHYSICAL PROPERTIES
PIGMENTS
PORPHYRINS
PROTEINS
REACTION INTERMEDIATES
REDUCTION
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
VERTEBRATES