Oleyl-ACP

These chain lengths may be maintained by the combined action of the three keto-acyl synthase enzymes (KAS I-III), and relatively specific thioesterases that convert acyl-ACP molecules to the corresponding CoA derivatives. Most plants have an acyl-ACP thioesterase with the highest activity for oleyl-ACP. Chain termination also may occur when fatty acids are transferred from ACP to glycerol-3-phosphate by acyltransferases (Ohlrogge et al., 1993) (see below). 

There was a strong preference for oleate over palmitate by the enzymes from spinach and pea. The specificity was the same both for acyl-CoAs and for acyl-ACPs although the latter is almost certainly the physiological substrate. This substrate specificity was reversed when the requirements for the second acylation reaction were studied, palmitate being almost exclusively used in the conversion of 1-oleyl-G-3-P to PA by enzymes localized on the chloroplast envelope. These specificities are entirely consistent with what we know of the fatty acid distribution of complex lipids of these two species. 

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