| Abstract
| - Alcohol acyltransferases (AAT) play a key role in the biosynthesis of ester aroma volatiles in fruit.Three ripening-specific recombinant AATs of cantaloupe Charentais melon fruit (Cm-AAT1, Cm-AAT3, and Cm-AAT4) are capable of synthesizing thioether esters with Cm-AAT1 being by far themost active. All proteins, as well as AAT(s) extracted from melon fruit, are active as tetramers ofaround 200 kDa. Kinetic analysis demonstrated that CoA-SH, a product of the reaction, is an activatorat low concentrations and an inhibitor at higher concentrations. This was confirmed by the additionof phosphotransacetylase at various concentrations, capable of modulating the level of CoA-SH inthe reaction medium. Site-directed mutagenesis of some amino acids that were specific to the Cm-AAT sequences into amino acids that were consensus to other characterized AATs greatly affectedthe selectivity of the original protein and the number of esters produced. Keywords: Cucumis melo; alcohol acyltransferases; sulfur-containing esters; aroma volatiles; site-directed mutagenesis
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