title: Developmental and varietal differences in volatile ester formation and acetyl-CoA: alcohol acetyl transferase activities in apple (Malus domestica Borkh.) fruit.
abstract: Apple (Malus domestica Borkh.) cultivars differ in their aroma and composition of volatile acetates in their fruit flesh and peel. Cv. Fuji flesh contains substantial levels of 2-methyl butyl acetate (fruity banana-like odor), while the flesh of cv. Granny Smith apples lacks this compound. Granny Smith apples accumulate mainly hexyl acetate (apple-pear odor) in their peel. Feeding experiments indicated that Fuji apples were able to convert hexanol and 2-methyl butanol to their respective acetate derivatives in vivo, while Granny Smith apples could only convert exogenous hexanol to hexyl acetate. Differential substrate specificities of the in vitro acetyl-CoA:alcohol acetyl transferase (AAT) activities were also detected among cultivars. In Granny Smith apples, the AAT activity was detected only in the peel, and its specificity was almost exclusively restricted to hexanol and cis-3-hexenol. In Fuji apples, the AAT activity was detected in both peel and flesh and apparently accepted a broader range of alcohols as substrates than the Granny Smith enzyme activity. Our data strongly suggest that different AAT activities are operational in apple tissues and cultivars and that these differences contribute to the variation observed in the accumulation of volatile acetates.
authors.affiliation: Institute of Field Crops and Horticulture, Agricultural Research Organization, Newe Ya'ar Research Center, Ramat Yishay 30095, Israel. dholland@int.gov.il
authors.forename: Doron
authors.initials: D
authors.lastname: Holland
authors.forename: Olga
authors.initials: O
authors.lastname: Larkov
authors.forename: Irit
authors.initials: I
authors.lastname: Bar-Ya'akov
authors.forename: Einat
authors.initials: E
authors.lastname: Bar
authors.forename: Alon
authors.initials: A
authors.lastname: Zax
authors.forename: Ester
authors.initials: E
authors.lastname: Brandeis
authors.forename: Uzi
authors.initials: U
authors.lastname: Ravid
authors.forename: Efraim
authors.initials: E
authors.lastname: Lewinsohn
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism*; D000123:Acetyltransferases / Q000378:metabolism*; D004952:Esters / Q000378:metabolism*; D005638:Fruit / Q000201:enzymology*; D008401:Gas Chromatography-Mass Spectrometry; D027845:Malus / Q000201:enzymology*; D014835:Volatilization
chemical_list: D004952:Esters; D000105:Acetyl Coenzyme A; D000123:Acetyltransferases