Novel pathways of oleic and cis-vaccenic acid biosynthesis by an enzymatic double-bond shifting reaction in higher plants.

The novel pathways of oleic acid formation from cis-vaccenic (cis-11-octadecenoic) acid and of cis-vaccenic acid formation from oleic acid by enzymatic positional isomerization have been proposed in higher plants, based on stable-isotope experiments using [2,2-2H2]cis-vaccenate or [2,2-2H2]oleate as an immediate precursor. A pulp homogenate and also pulp slices prepared from developing kaki (Diospyros kaki) fruit could catalyze these hitherto unknown isomerizations. This suggests the presence of a new type of isomerase responsible for the double-bond shifting reaction without cis-trans isomerization in the middle of fatty acid carbon chains.