title: Characterization and subcellular localization of chlorophyllase from Ginkgo biloba.
abstract: Chlorophyllase (Chlase) catalyzes the initial step of chlorophyll (Chl)-degradation, but the physiological significance of this reaction is still ambiguous. Common understanding of its role is that Chlase is involved in de-greening processes such as fruit ripening, leaf senescence, and flowering. But there is a possibility that Chlase is also involved in turnover and homeostasis of Chls. Among the de-greening processes, autumnal coloration is one of the most striking natural phenomena, but the involvement of Chlase during autumnal coloration is not clear. Previously, it was shown that Chlase activity and expression level of the Chlase gene were not increased during autumnal coloration in Ginkgo biloba, indicating that Chlase does not work specially in the de-greening processes in G. biloba. In this study, we characterized the recombinant Chlase and analyzed its subcellular localization to understand the role of the cloned Chlase of G. biloba (GbCLH). GbCLH exhibited its highest activity at pH 7.5, 40 degrees C. Kinetic analysis revealed that GbCLH hydrolyzes pheophytin (Pheo) a and Chl a more rapidly than Pheo b and Chl b. Transient expression analysis of 40 N-terminus amino acids of GbCLH fused with GFP (green fluorescent protein) and subcellular fractionation showed that GbCLH localizes within chloroplasts. Together with our previous results, property of GbCLH and its location within the chloroplasts suggest that GbCLH plays a role in the turnover and homeostasis of Chls in green leaves of G. biloba.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. okazawa@bio.eng.osaka-u.ac.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Okazawa
authors.forename: Lei
authors.initials: L
authors.lastname: Tango
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Itoh
authors.forename: Ei'ichiro
authors.initials: E
authors.lastname: Fukusaki
authors.forename: Akio
authors.initials: A
authors.lastname: Kobayashi
mesh_terms: D000595:Amino Acid Sequence; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004926:Escherichia coli; D020441:Ginkgo biloba / Q000201:enzymology*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D011994:Recombinant Proteins; D002265:Carboxylic Ester Hydrolases; C019875:chlorophyllase