Photometric characteristics of haem proteins in erythropoietin-producing hepatoma cells (HepG2)

• Published in: Biochemical journal 1993-03, Vol.290 (3), p.771-776
• Main Authors: GÖRLACH, A, HOLTERMANN, G, JELKMANN, W, HANCOCK, J. T, JONES, S. A, JONES, O. T. G, ACKER, H
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Biological and medical sciences; Blotting, Western; Carcinoma, Hepatocellular - chemistry; Erythropoietin - biosynthesis; Fundamental and applied biological sciences. Psychology; Hemeproteins - chemistry; Hemeproteins - metabolism; Humans; Hydrogen Peroxide - metabolism; Liver Neoplasms - chemistry; NADH, NADPH Oxidoreductases - metabolism; NADPH Oxidases; Oxygen - analysis; Oxygen - metabolism; Potassium Cyanide - pharmacology; Potentiometry; Protein hormones. Growth factors. Cytokines; Proteins; Spectrophotometry; Tumor Cells, Cultured
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2900771

Erythropoietin (Epo)-producing hepatoma cells (HepG2) reveal, in addition to the cytochromes of the respiratory chain, a photometrically measurable haem signal with absorbance maxima at 559 nm and 427 nm, suggesting the presence of a b-type cytochrome. This activity exhibited a low midpoint potential, CO-binding spectra and reduction which was insensitive to both cyanide and antimycin. This haem possessed a 22 kDa subunit and might be part of an electron transfer chain similar to the NADPH oxidase, since the NADPH oxidase cytosolic activating factor (p47) could be identified by Western blot analysis. H2O2, which was detected inside the cells by confocal microscopy, might therefore be produced by the suggested electron transfer chain. This cyanide- and antimycin-insensitive but hypoxia-sensitive cytochrome b would be an attractive candidate for controlled Epo production in response to pO2.