Fatty acid degradation is thought to contribute to the formation of short chain fatty acids and aldehydes to yield straight-chain esters.
Although β-oxidation of fatty acids has been established as one of the primary processes contributing to the pool of alcohols and acyl-CoA for ester production, unsaturated straight-chain esters appear to arise only by the LOX pathway.
A recent study from Lavis's group showed that cytosolic esterases have high activity toward straight-chain esters and the hydrolyzed products of those esters can be detected within 30 min in different cell lines tested.
The resulting alcohols are linked to an acyl moiety by alcohol acyl-CoA transferases (AATs) to form esters. Unsaturated straight-chain esters appear to arise mainly by the LOX pathway in apple.
Thus, LOX1 Md 1a is suggested to be involved in the generation of C6 aldehydes (primarily hexanal in the case of apple) and the formation of hexyl and possibly other straight-chain esters in intact, ripening fruit whereas other LOXs primarily take part in the production of 'green note' aldehydes.
We assume that saturated and mono-unsaturated fatty acids are primarily degraded by β-oxidation in intact fruit, thus providing precursors for short, straight-chain esters, whereas the late steps of the β-oxidation process for polyunsaturated fatty acids such as LA and LnA are impaired.
In combination with previous literature on kinetic properties of the enzyme, our studies suggest that these residues determine the unique specificity of the TmAcE for short straight chain esters.
Straight-chain alcohols, aldehydes, ketones, acids, esters and lactones are primarily formed by the fatty acid oxidation pathway by lipoxygenase, via α and β- oxidation.
In tea plants, we identified many fatty acid-derived straight-chain alcohols, aldehydes, ketones, acids, esters and lactones, which are formed by three basic processes: α -oxidation, β-oxidation and the lipoxygenation.
Bacterial and eukaryotic membranes are primarily composed of ester-linked, straight-chain fatty acids and utilize glycerol-3-phosphate lipids, whereas archaea have ether-linked fatty acids derived from highly methyl-branched isoprenoids and utilize a glycerol-1-phosphate backbone [ 114].
