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Title: Interference by morpholine ethanesulfonic acid (MES) and related buffers in phenolic oxidation by peroxidase

Author
item Baker, Con
item Mock, Norton
item Roberts, Daniel
item Deahl, Kenneth
item Hapeman, Cathleen
item Schmidt, Walter
item Kochansky, Jan

Submitted to: Biochemical and Biophysical Research Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2007
Publication Date: 8/1/2007
Citation: Baker, C.J., Mock, N.M., Roberts, D.P., Deahl, K.L., Hapeman, C.J., Schmidt, W.F., Kochansky, J.P. 2007. Interference by morpholine ethanesulfonic acid (MES) and related buffers in phenolic oxidation by peroxidase. Biochemical and Biophysical Research Communications. 43:1322-1327.

Interpretive Summary: Plant diseases cause major losses to farmers each year. Better understanding of the biochemical basis for plant resistance to disease will lead to improved strategies to improve plant health and reduce losses. In this paper we report the discovery that a commonly used laboratory biological buffer (a chemical that prevents a solution from becoming acidic) can alter certain important biochemical processes. It is possible that these alterations would change the behavior (e.g. growth, germination, disease resistance) of the model system in the laboratory and lead to misunderstanding of how the system behaves in the field. By being aware of this problem, scientists can check to see if the buffer affects their system and use an alternate buffer if necessary. This information will be of use to plant scientists who are devising new strategies to improve disease resistance in plants.

Technical Abstract: While characterizing the kinetic parameters of apoplastic phenolic oxidation by peroxidase, we found anomalies caused by the 4-morpholine ethanesulfonic acid (MES) buffer being used. In the presence of MES, certain phenolics appeared not to be oxidized by peroxidase, yet the oxidant, H2O2, was utilized. This anomaly appears to be due to the recycling of the phenolic substrate. The reaction is relatively inefficient, but at buffer concentrations of 10 mM or greater the recycling effect is nearly 100% with substrate concentrations less than 100 M. The effect is substrate specific, occurring with hydroxyacetophenone but not with dimethoxy-hydroxyacetophenone (acetosyringone). Characterization of the reaction parameters suggests that MES interacts with the oxidized phenolic causing its reduction. Similar responses occurred with related buffers such as hydroxyethyl piperazine ethanesulfonic acid (HEPES) and piperazine ethanesulfonic acid (PIPES).