During the first year of the project initial evidence for the presence of carotenoid cleavage enzymes was observed in the leaves of two grape varieties commonly grown in Germany, Riesling and Silvaner. A crude enzyme extract was obtained and the enzyme was shown to have an estimated isolectric point of pH 3-4.
In several fruits and vegetables, carotenoid cleavage enzymes have been shown to be involved in degradation of carotenoids to produce important flavor compounds, including C13-norisoprenoids. However, the role of these enzymes in development of grape flavor is unknown. Therefore, the overall goal of the research project initiated during the study visit is to focus on the role that carotenoid cleavage enzymes play in norisoprenoid formation in grapes and grape leaves. In order to reach this goal our specific objectives are to:
- Confirm the presence of carotenoid cleavage enzymes in grapes and grape leaves
- Characterize the carotenoid cleavage enzyme with respect to pH and temperature optima, molecular weight, number of subunits, etc.
- Utilize isolated carotenoid cleavage enzyme (or partially purified enzyme fractions) in biomimetic studies to examine pathways of C13-norisoprenoid flavor production.