title: Structural characteristics of green tea catechins for formation of protein carbonyl in human serum albumin.
abstract: Catechins are polyphenolic antioxidants found in green tea leaves. Recent studies have reported that various polyphenolic compounds, including catechins, cause protein carbonyl formation in proteins via their pro-oxidant actions. In this study, we evaluate the formation of protein carbonyl in human serum albumin (HSA) by tea catechins and investigate the relationship between catechin chemical structure and its pro-oxidant property. To assess the formation of protein carbonyl in HSA, HSA was incubated with four individual catechins under physiological conditions to generate biotin-LC-hydrazide labeled protein carbonyls. Comparison of catechins using Western blotting revealed that the formation of protein carbonyl in HSA was higher for pyrogallol-type catechins than the corresponding catechol-type catechins. In addition, the formation of protein carbonyl was also found to be higher for the catechins having a galloyl group than the corresponding catechins lacking a galloyl group. The importance of the pyrogallol structural motif in the B-ring and the galloyl group was confirmed using methylated catechins and phenolic acids. These results indicate that the most important structural element contributing to the formation of protein carbonyl in HSA by tea catechins is the pyrogallol structural motif in the B-ring, followed by the galloyl group. The oxidation stability and binding affinity of tea catechins with proteins are responsible for the formation of protein carbonyl, and consequently the difference in these properties of each catechin may contribute to the magnitude of their biological activities.
authors.affiliation: Department of Food and Nutritional Sciences, and Global Center of Excellence (COE) Program, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan. ishii_t@u-shizuoka-ken.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ishii
authors.forename: Taiki
authors.initials: T
authors.lastname: Mori
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Maiko
authors.initials: M
authors.lastname: Kaku
authors.forename: Koji
authors.initials: K
authors.lastname: Kusaka
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Uekusa
authors.forename: Mitsugu
authors.initials: M
authors.lastname: Akagawa
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Aihara
authors.forename: Takumi
authors.initials: T
authors.lastname: Furuta
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Wakimoto
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kan
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakayama
mesh_terms: D002392:Catechin / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D015394:Molecular Structure; D050050:Protein Carbonylation; D011748:Pyrogallol / Q000737:chemistry / Q000378:metabolism; D012709:Serum Albumin / Q000378:metabolism*; D013662:Tea / Q000737:chemistry / Q000378:metabolism*
chemical_list: D012709:Serum Albumin; D013662:Tea; D011748:Pyrogallol; D002392:Catechin