Received for review July 15, 2004. Revised manuscript received October 26, 2004. Accepted November 2, 2004. This study was supported by grants from BRAIN.

Abstract:

Thioredoxin (TRX) is an important antioxidant present in all types of organisms. Besides its role as an antioxidant, TRX protects the gastric mucosa due to its antiinflammatory effect. In addition, TRX decreases allergenicity; therefore, the oral administration of TRX is of considerable interest with respect to its clinical use as well as the development of functional foods containing TRX. We have attempted to enrich the cellular TRX content in Saccharomyces cerevisiae, and found that green tea extract (Sunphenon), which is rich in catechins (polyphenols), activates the Yap1 transcription factor, leading to the induction of TRX2, a target of Yap1. Production of yeast TRX was monitored by both a TRX2-lacZ reporter expression assay and Western blotting using an anti-yeast TRX antibody. Maximal production of TRX was achieved in a medium containing 0.1% green tea extract at pH 7.6. We discuss the underlying mechanism by which green tea extract activates Yap1.

Keywords: Thioredoxin; green tea extract; epigallocatechin gallate; Yap1; yeast; antioxidant; polyphenol; catechin

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