TAILIEUCHUNG - Báo cáo khoa học: An inserted loop region of stromal ascorbate peroxidase is involved in its hydrogen peroxide-mediated inactivation

Ascorbate peroxidase isoforms localized in the stroma and thylakoid of higher plant chloroplasts are rapidly inactivated by hydrogen peroxide if the second substrate, ascorbate, is depleted. However, cytosolic and micro-body-localized isoforms from higher plants as well as ascorbate peroxidase B, an ascorbate peroxidase of a red algaGaldieria partita, are relatively tolerant. | iFEBS Journal An inserted loop region of stromal ascorbate peroxidase is involved in its hydrogen peroxide-mediated inactivation Sakihito Kitajima1 Ken-ichi Tomizawa1 Shigeru Shigeoka2 and Akiho Yokota3 1 Research Institute of Innovative Technology for the Earth RITE Soraku-gun Kyoto Japan 2 Department of Food and Nutrition Faculty of Agriculture Kinki University Nakamachi Nara Japan 3 Graduate Schoolof BiologicalScience Nara Institute of Science and Technology NAIST Ikoma Japan Keywords ascorbate peroxidase chloroplast Galdieria partita hydrogen peroxide inactivation Correspondence A. Yokota Graduate School of Biological Science Nara Institute of Science and Technology NAIST Ikoma Nara 630-0192 Japan Fax 81 774 75 2320 Tel 81 774 75 2307 E-mail yokota@ Present address Graduate School of Science and Technology Kyoto Institute of Technology Matsugasaki Sakyo-ku Kyoto 606-8585 Japan Received 18 February 2006 revised 13 April2006 accepted 20 April 2006 doi Ascorbate peroxidase isoforms localized in the stroma and thylakoid of higher plant chloroplasts are rapidly inactivated by hydrogen peroxide if the second substrate ascorbate is depleted. However cytosolic and microbody-localized isoforms from higher plants as well as ascorbate peroxidase B an ascorbate peroxidase of a red alga Galdieria partita are relatively tolerant. We constructed various chimeric ascorbate peroxidases in which regions of ascorbate peroxidase B from sites internal to the C-terminal end were exchanged with corresponding regions of the stromal ascorbate peroxidase of spinach. Analysis of these showed that a region between residues 245 and 287 was involved in the inactivation by hydrogen peroxide. A 16-residue amino acid sequence 249-264 found in this region of the stromal ascorbate peroxidase was not found in other ascorbate peroxidase isoforms. A chimeric ascorbate peroxidase B with this sequence inserted was inactivated by hydrogen peroxide within

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