tailieunhanh - Báo cáo khoa học: Protein expressed by the ho2 gene of the cyanobacterium Synechocystis sp. PCC 6803 is a true heme oxygenase

Two isoforms of a heme oxygenase gene,ho1andho2, with 51% identity in amino acid sequence have been identified in the cyanobacterium Synechocystissp. PCC 6803. Isoform-1, Syn HO-1, has been characterized, while isoform-2, Syn HO-2, has not. In this study, a full-lengthho2gene was cloned using synthetic DNA and Syn HO-2 was demonstrated to be highly expressed inEscherichia colias a soluble, catalytically active protein. Like Syn HO-1, the purified Syn HO-2 bound hemin stoichiometrically to form a heme–enzyme complex and degraded heme to biliverdin IXa,CO and iron in the presence of reducing systems such as NADPH⁄ferredoxin reductase⁄ferredoxin and sodium ascorbate. . | iFEBS Journal Protein expressed by the ho2 gene of the cyanobacterium Synechocystis sp. PCC 6803 is a true heme oxygenase Properties of the heme and enzyme complex Xuhong Zhang1 Catharina T. Migita2 Michihiko Sato3 Masanao Sasahara1 and Tadashi Yoshida1 1 Department of Biochemistry Yamagata University Schoolof Medicine Japan 2 Department of BiologicalChemistry Faculty of Agriculture Yamaguchi University Japan 3 CentralLaboratory for Research and Education Yamagata University Schoolof Medicine Japan Keywords biliverdin cyanobacterium heme oxygenase EPR ferredoxin heme oxygenase Correspondence T. Yoshida Department of Biochemistry Yamagata University Schoolof Medicine Iida-nishi 2-2-2 Yamagata 990-9585 Japan Fax 81 23 6285225 Tel 81 23 6285222 E-mail tyoshida@ Received 25 August 2004 revised 10 December 2004 accepted 17 December 2004 doi Two isoforms of a heme oxygenase gene hoi and ho2 with 51 identity in amino acid sequence have been identified in the cyanobacterium Synechocystis sp. PCC 6803. Isoform-1 Syn HO-1 has been characterized while isoform-2 Syn HO-2 has not. In this study a full-length ho2 gene was cloned using synthetic DNA and Syn HO-2 was demonstrated to be highly expressed in Escherichia coli as a soluble catalytically active protein. Like Syn HO-1 the purified Syn HO-2 bound hemin stoichiometrically to form a heme-enzyme complex and degraded heme to biliverdin IXa CO and iron in the presence of reducing systems such as NADPH ferredoxin reductase ferredoxin and sodium ascorbate. The activity of Syn HO-2 was found to be comparable to that of Syn HO-1 by measuring the amount of bilirubin formed. In the reaction with hydrogen peroxide Syn HO-2 converted heme to verdoheme. This shows that during the conversion of hemin to a-meso-hydroxyhemin hydroperoxo species is the activated oxygen species as in other heme oxygenase reactions. The absorption spectrum of the hemin-Syn HO-2 complex at neutral pH .