Electron paramagnetic resonance studies on cytochrome b-558 and peroxidases of pig blood granulocytes.
Low-temperature electron paramagnetic resonance (EPR) spectrometry on granulocytes prepared from pig blood was carried out with concentrated cellular and subcellular fractions to characterize EPR signals of cytochrome b-558 (cyt b-558). A thick cell suspension (approximately 2 x 10(9) cells/ml), containing mostly neutrophils, showed typical high-spin EPR signals due to myeloperoxidase (MPO) and a low spin signal at a g value of around 3.2. A similar thick granulocyte suspension containing eosinophils showed not only these signals but also low spin heme signals at g values of 2.86, 2.13, and 1.66, which have been reported to be of cyt b-558 (Ueno et al. 1991, FEBS Lett. 281, 130-132). MPO and eosinophil peroxidase (EPO) were released from the membrane fractions with 50 mM phosphate buffer (pH 7.0) containing 1 M NaCl, and then were highly concentrated, in which no cyt b-558 was detected by absorption spectra. The signal at a g value of 2.86 was found only in the EPO fraction, suggesting that this signal is derived from a low-spin form of an EPO-complex, but neither from MPO nor cyt b-558. The O2(-)-forming NADPH oxidase associated in the membranes was solubilized with heptyl-thio-glucoside at 0 degree C and concentrated up to 45 microM cyt b-558 with no modification of the heme moiety confirmed by its O2(-)-generating activity and lack of carbon monoxide-binding capacity. Cyt b-558 showed an anisotropic signal at a g value of 3.2 +/- 0.05, which was cyanide-insensitive and reducible with reductants. The signal intensity was concentration dependent, suggesting that the g = 3.2 signal is characteristic of the low-spin heme iron in cyt b-558.
Fujii
H
H
Department of Inflammation Research, Tokyo Metropolitan Institute of Medical Science, Japan.
Kakinuma
K
K
D000818:Animals; D003573:Cytochrome b Group / Q000097:blood* / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D047209:Eosinophil Peroxidase; D006098:Granulocytes / Q000737:chemistry / Q000201:enzymology*; D019255:NADPH Oxidases; D009195:Peroxidase / Q000097:blood; D010544:Peroxidases / Q000097:blood* / Q000737:chemistry; D013053:Spectrophotometry; D013347:Subcellular Fractions / Q000201:enzymology; D013552:Swine
D003573:Cytochrome b Group; C036888:cytochrome b558; D047209:Eosinophil Peroxidase; D010544:Peroxidases; D009195:Peroxidase; D019255:NADPH Oxidases