| Abstract
| - To modify the flavor properties of tomato fruits, cucumber fatty acid hydroperoxide lyase (HPL),which can act on 9-hydroperoxides of fatty acids to form volatile C9-aldehydes, was introduced totomato plants. Through enzyme assay, high activity of the introduced HPL could be found in eitherthe leaves or fruits of transgenic tomatoes; however, the composition of volatile short-chain aldehydesand alcohols in the transgenic tomato fruits was little modified. This was unexpected because tomatofruits have high lipoxygenase activity to form 9-hydroperoxides. When linoleic acid was added to acrude homogenate prepared from the transgenic tomato fruits, a high amount of C9-aldehyde wasformed, but the amount of C6-aldehyde was almost equivalent to that in nontransgenic tomatoes.Through quantification of fatty acid hydroperoxides, it has been revealed that 13-hydroperoxides offatty acids are preferably formed from endogenous substrate, whereas 9-hydroperoxides are formedfrom fatty acids added exogenously. From these observations, possible mechanisms to regulatemetabolic flow of the lyase pathway are discussed. Keywords: Tomato (Lycopersicon esculentum Mill.); volatile aldehydes; fatty acid hydroperoxidelyase; lipoxygenase
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