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An efficient bacterial expression system of cyanobacterium Synechocystissp. PCC 6803 heme oxygenase gene, ho-1, has been constructed, using a synthetic gene. A soluble protein was expressedat high levels and was highly purified, for the first time. The protein binds equimolar free hemin to catabolize the boundhemin to ferric-bili-verdin IXa in the presence of oxygen andreducing equivalents, showing the heme oxygenase activity. During the reaction, verdoheme intermediate is formed with the evolution of carbon monoxide. . | Eur. J. Biochem. 270 687-698 2003 FEBS 2003 doi 10.1046 j.1432-1033.2003.03421.x Expression and characterization of cyanobacterium heme oxygenase a key enzyme in the phycobilin synthesis Properties of the heme complex of recombinant active enzyme Catharina T. Migita1 Xuhong Zhang2 and Tadashi Yoshida2 1Department of Biological Chemistry Faculty of Agriculture Yamaguchi University Japan department of Biochemistry Yamagata University School of Medicine Japan An efficient bacterial expression system of cyanobacterium Synechocystis sp. PCC 6803 heme oxygenase gene ho-1 has been constructed using a synthetic gene. A soluble protein was expressed at gigh levels and was hiyhly purified for the first time. The protein binds equimolar free hemin to catabolize the bound hemin to I erric-bi-i-verdin IXa in the presence of oxygen and reducing equivalents showing the heme oxygenase activity. During the reaction verdoheme intermediate is formed with the evolution of carbon monoxide. Though both ascorbate and ADDPH-cylochrome 4450 reductase verve as an electron donor the heme catabolism assisted by ascorbate is considerably slow and the reaction with NADPP-cytochrome P450 reductase is greatly retarded after the oxy-heme complex formation. The optical absorption spectra of the heme-enzyme complexes are similar to those of the known heme oxygenase complexes but have some distinct features exhibiting the Soret band slightly blue-shifted nitel Ế la il ely mong TT ndnds of the high-spin component in the ferric form spectrum. The hemeenzyme complex shows the acid-base transition where two alkaline species aee geneeated. EPR of the niteosyl heme complex has established die nitr cnanous proximal ligand peesumably histidine 17 and the obtained EPR parameters are discriminated from those of the rat heme oxygenase-1 complex. The spectroscopic characters as well as the catabolic activities strongly suggest that in spite of very high conservation of the primary structure the heme pocket .
