Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 445868
Title The anti-browning agent sulfite inactivates Agaricus bisporus tyrosinase through covalent modification of the copper-B site
Author(s) Kuijpers, T.F.M.; Gruppen, H.; Sforza, S.; Berkel, W.J.H. van; Vincken, J.P.
Source FEBS Journal 280 (2013)23. - ISSN 1742-464X - p. 6184 - 6195.
DOI https://doi.org/10.1111/febs.12539
Department(s) Food Chemistry Group
Biochemistry
VLAG
Publication type Refereed Article in a scientific journal
Publication year 2013
Keyword(s) glutathione conjugate formation - crystal-structure - mushroom tyrosinase - polyphenol oxidase - chlorogenic acid - plant - inhibition - metabolism - thioether - sequence
Abstract Sulfite salts are widely used as antibrowning agents in food processing. Nevertheless, the exact mechanism by which sulfite prevents enzymatic browning has remained unknown. Here, we show that sodium hydrogen sulfite (NaHSO3 ) irreversibly blocks the active site of tyrosinase from the edible mushroom Agaricus bisporus, and that the competitive inhibitors tropolone and kojic acid protect the enzyme from NaHSO3 inactivation. LC-MS analysis of pepsin digests of NaHSO3 -treated tyrosinase revealed two peptides showing a neutral loss corresponding to the mass of SO3 upon MS(2) fragmentation. These peptides were found to be homologous peptides containing two of the three histidine residues that form the copper-B-binding site of mushroom tyrosinase isoform PPO3 and mushroom tyrosinase isoform PPO4, which were both present in the tyrosinase preparation used. Peptides showing this neutral loss behavior were not found in the untreated control. Comparison of the effects of NaHSO3 on apo-tyrosinase and holo-tyrosinase indicated that inactivation is facilitated by the active site copper ions. These data provide compelling evidence that inactivation of mushroom tyrosinase by NaHSO3 occurs through covalent modification of a single amino-acid residue, probably via addition of HSO3 (-) to one of the copper-coordinating histidines in the copper-B site of the enzyme
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