A Comparative Study of the Oxygen Transport Proteins of Dendrostomum pyroides

Reduction of methemerythrin by deoxymyoglobin: a protein-protein redox reaction not involving electron-transfer proteins

“…The marine worms P. gouldii and T. pyroides were obtained, respectively, from Marine Biological Laboratory, Woods Hole, MA, and Pacific Biomarine Supply, Venice, CA. Oxyhemerythrin was obtained from the coelomic fluid of these worms by the methods of Klotz et al (1957) and Klippenstein et al (1972). Metmyohemerythrin was obtained directly from the retractor muscles of T. pyroides by a modification of the procedure of Klippenstein et al (1972), omitting the addition of azide.…”

“…Oxyhemerythrin was obtained from the coelomic fluid of these worms by the methods of Klotz et al (1957) and Klippenstein et al (1972). Metmyohemerythrin was obtained directly from the retractor muscles of T. pyroides by a modification of the procedure of Klippenstein et al (1972), omitting the addition of azide. Methemerythrin was prepared from oxyhemerythrin by adding 2-3 molar excess of Fe(CN)63or by dialyzing against 1 mM Fe(CN)63~.…”

Proteins containing oxo-bridged dinuclear iron centers: a bioinorganic perspective

“…13,14 The most detailed information on the structure and function of hemerythrin has come from X-ray crystallographic studies.15"29 Each subunit of Hr is composed of four antiparallel a-helices (Figure 1), which comprise approximately 75% of the amino acid residues (in agreement with predictions of earlier circular dichroism studies). 30,31 The virtually identical tertiary structures of subunits from proteins of varying sources is somewhat surprising, given the fact that there is only approximately 40% sequence homology,32 35 a situation reminiscent of hemoglobin and myoglobin. Two iron atoms are bound in a dinuclear iron center, which is located roughly in the center of the four a-helices.…”

Chemical mechanisms of catalysis by cytochromes P-450: a unified view

“…(5) Oxidative group transfer involves a 1,2 carbon shift of a group with concomitant incorporation of oxygen 0001-4842/84/0117-0009$01.50/0 as a carbonyl at the C-l position. (6) Olefinic suicide destruction involves inactivation of the heme, in our considerations here, of cytochrome P-450 by an enzyme product or an enzyme intermediate. Other reactions catalyzed by cytochromes P-450, which will not be considered here, include the reduction of azo dyes, epoxides, iV-oxides, and halomethanes, the reduction and scission of hydroperoxides (and propagation of lipid peroxidation), and relatively nonspecific oxidations involving forms of partially reduced oxygen that can be released from cytochrome P-450.…”

“…The early steps in the cytochrome P-450 catalytic cycle are shown in Figure l. [3][4][5][6] The binding of the substrate to the ferric enzyme is rapid and stoichiometric. 7 In some cases the iron is changed from the lowto high-spin state and the oxidation-reduction potential is raised upon binding.8 Our own studies with the liver microsomal cytochromes P-450 indicate that these changes are not always observed and are not related to rates of catalysis.6,9 The substrate-bound ferric enzyme accepts one electron from the flavoprotein NADPH-cytochrome P-450 reductase,9,10 which contains one FMN and one FAD,11 and which donates the electron from the FMNH2/FADH• complex.…”