title: Differential activities of fungi-derived tannases on biotransformation and substrate inhibition in green tea extract.
abstract: Tannases are important enzymes in the antioxidant potential of tea leaves. In this study, we evaluated the effect of two tannases (T1 and T2) on biotransformation of tea polyphenols and antioxidative activities from catechins in green tea extract (GTE). The T1 tannase-catalyzed reaction was inhibited by the addition of >2.0% GTE substrate, whereas the T2-catalyzed reaction was not inhibited, even by addition of 5.0% GTE. Furthermore, the T1 tannase-catalyzed reaction was inhibited by addition of 10 mg mL(-1) EGCG, whereas the T2 tannase-catalyzed reaction did not display any inhibitory effect. These results indicate that T2 tannase was more tolerant than T1 tannase to substrate inhibition in degallation reactions. Specifically, the substrate EGCG (90,687.1 μg mL(-1)) was transformed into gallic acid (50,242.9 μg mL(-1)) and EGC (92,598.3 μg mL(-1)) after 1-h treatment with T2 tannase (500 U g(-1)). The tannase-mediated product displayed higher in vitro radical-scavenging activity than the control. IC50 value of GTE on ABTS and DPPH radicals (46.1 μg mL(-1) and 18.4 μg mL(-1), respectively) decreased markedly after T2 tannase treatment (to 35.8 μg mL(-1) and 15.1 μg mL(-1), respectively). These results indicate that T2 tannase treatment of GTE enhanced its radical-scavenging activity, an increase that was also observed in the reaction using EGCG substrate. Taken together, our results revealed that T2 tannase is more suitable for biotransformation of catechins in GTE than T1 tannase, and T2 treatment provides an enhanced radical-scavenging effect.
authors.affiliation: Cosmax Bio INC, Jecheon 390-250, Republic of Korea.
authors.forename: Joo Hyun
authors.initials: JH
authors.lastname: Baik
authors.affiliation: Department of Food and Nutrition, Korea University, Seoul 136-703, Republic of Korea; Department of Public Health Science, Graduate School, Korea University, Seoul 136-7033, Republic of Korea.
authors.forename: Hyung Joo
authors.initials: HJ
authors.lastname: Suh
authors.affiliation: Department of Food and Nutrition, Korea University, Seoul 136-703, Republic of Korea.
authors.forename: So Young
authors.initials: SY
authors.lastname: Cho
authors.affiliation: Department of Food and Nutrition, Korea University, Seoul 136-703, Republic of Korea.
authors.forename: Yooheon
authors.initials: Y
authors.lastname: Park
authors.affiliation: Department of Food and Nutrition, Korea University, Seoul 136-703, Republic of Korea. Electronic address: sirchoi@hanmail.net.
authors.forename: Hyeon-Son
authors.initials: HS
authors.lastname: Choi
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D055162:Biocatalysis / Q000187:drug effects; D001711:Biotransformation; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000378:metabolism; D005658:Fungi / Q000201:enzymology*; D005707:Gallic Acid / Q000378:metabolism / Q000494:pharmacology; D006868:Hydrolysis / Q000187:drug effects; D010936:Plant Extracts / Q000737:chemistry* / Q000378:metabolism*; D059808:Polyphenols / Q000378:metabolism; D013662:Tea / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D010936:Plant Extracts; D059808:Polyphenols; D013662:Tea; D005707:Gallic Acid; D002392:Catechin; C045651:epigallocatechin gallate; D002265:Carboxylic Ester Hydrolases; C022711:tannase
keywords: Antioxidative activity; Biotransformation; Substrate inhibition; Tannase; Tea catechins