Finding flavor genes

A key enzyme involved in flavor biogenesis in ripening strawberries has been discovered using customized cDNA microarrays.
Identification of the SAAT Gene Involved in Strawberry Flavor Biogenesis by Use of DNA Microarrays
Fruit flavor is a result of a complex mixture of numerous compounds. The formation of these compounds is closely correlated with the metabolic changes occurring during fruit maturation. Here, we describe the use of DNA microarrays and appropriate statistical analyses to dissect a complex developmental process. In doing so, we have identified a novel strawberry alcohol acyltransferase (SAAT) gene that plays a crucial role in flavor biogenesis in ripening fruit. Volatile esters are quantitatively and qualitatively the most important compounds providing fruity odors. Biochemical evidence for involvement of the SAAT gene in formation of fruity esters is provided by characterizing the recombinant protein expressed in Escherichia coli. The SAAT enzyme showed maximum activity with aliphatic medium-chain alcohols, whose corresponding esters are major components of strawberry volatiles. The enzyme was capable of utilizing short- and medium-chain, branched, and aromatic acyl-CoA molecules as cosubstrates. The results suggest that the formation of volatile esters in fruit is subject to the availability of acyl-CoA molecules and alcohol substrates and is dictated by the temporal expression pattern of the SAAT gene(s) and substrate specificity of the SAAT enzyme(s).
Partial purification and some properties of alcohol acyltransferase from strawberry fruits
The enzyme system concerning volatile ester formation in strawberry Fragaria ananassa×Duchessne var. Chandler was studied. Protein with alcohol acyltransferase activity was purified about 29-fold from Chandler strawberry fruits by ammonium sulfate fractionation, gel filtration, and anion-exchange chromatography. The enzyme activity had a pH optimum of 8.0 and an optimum temperature of 35 o C. The apparent M r estimated by gel filtration was 70 000. The enzyme was tested for its preference in using different acyl-CoAs and alcohols. Maximum activity was obtained using acetyl-CoA and hexyl alcohol as substrates. A clear correlation was observed between substrate preference and volatile esters present in strawberry var. Chandler