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Updated: Apr 15, 2026

The Terroir Concept Interpreted through Grape Berry Metabolomics and Transcriptomics
Published on: October 5, 2016
Polyphenoloxidase from Riesling and Dornfelder wine grapes (Vitis vinifera) is a tyrosinase
Petra Fronk1, Hermann Hartmann1, Margarita Bauer1
1Institute for Molecular Biophysics, Johannes Gutenberg-University Mainz, Jakob-Welder-Weg 26, 55128 Mainz, Germany.
Abstract:
Polyphenoloxidases (PPO) of the type-3 copper protein family are considered to be catecholoxidases catalyzing the oxidation of o-diphenols to their corresponding quinones. PPO from Grenache grapes has recently been reported to display only diphenolase activity. In contrast, we have characterized PPOs from Dornfelder and Riesling grapes which display both monophenolase and diphenolase activity. Ultracentrifugation and size exclusion chromatography indicated that both PPOs occur as monomers with Mr of about 38kDa. Non-reducing SDS-PAGE shows two bands of about 38kDa exhibiting strong activity. Remarkably, three bands up to 60kDa displayed only very weak PPO activity, supporting the hypothesis that the C-terminal domain covers the entrance to the active site. Molecular dynamic analysis indicated that the hydroxyl group of monophenolic substrates can bind to CuA after the flexible but sterically hindering Phe 259 swings away on a picosecond time scale.
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