Biochemical and catalytic properties of three recombinant alcohol acyltransferases of melon. sulfur-containing ester formation, regulatory role of CoA-SH in activity, and sequence elements conferring substrate preference.
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 the most active. All proteins, as well as AAT(s) extracted from melon fruit, are active as tetramers of around 200 kDa. Kinetic analysis demonstrated that CoA-SH, a product of the reaction, is an activator at low concentrations and an inhibitor at higher concentrations. This was confirmed by the addition of phosphotransacetylase at various concentrations, capable of modulating the level of CoA-SH in the 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 affected the selectivity of the original protein and the number of esters produced.
Lucchetta
Luciano
L
INRA/INP-ENSAT, UMR990 Génomique et Biotechnologie des fruits, Castanet, Tolosan, France.
Manriquez
Daniel
D
El-Sharkawy
Islam
I
Flores
Francisco-Borja
FB
Sanchez-Bel
Paloma
P
Zouine
Mohamed
M
Ginies
Christian
C
Bouzayen
Mondher
M
Rombaldi
Cesar
C
Pech
Jean-Claude
JC
Latché
Alain
A
D000217:Acyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000438:Alcohols / Q000378:metabolism*; D000595:Amino Acid Sequence; D003065:Coenzyme A / Q000502:physiology*; D019662:Cucurbitaceae / Q000201:enzymology*; D005638:Fruit / Q000201:enzymology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D000438:Alcohols; D011994:Recombinant Proteins; D000217:Acyltransferases; D003065:Coenzyme A