Biotin-like activity of positional and stereoisomers of octadecenoic acids.

A number of microorganisms have been investigated which require some particular fatty acid in addition to biotin as a growth factor (l-6). On the other hand, a large group of organisms are able to utilize certain fatty acids in place of biotin in the medium (7-11). Axelrod and coworkers (12, 13) reported that the saponifiable fraction from blood plasma possesses high biotin activity. This extract was later shown (Axelrod et al. (14)) to be composed of oleic, linoleic, arachidonic, and saturated acids; the latter exhibited no biotin-like activity for microorganisms but greatly enhanced the response to the unsaturated fraction. Trager (15) found that this lipide fraction of plasma, when injected into chicks, reduces t,he severity of dermatitis caused by a biotin deficiency induced by feeding a diet high in raw egg white. This biotin-sparing activity of the plasma lipide could not be duplicated by the injection of oleic acid, nor could it be brought about by the oral administration of the fat-soluble material from plasma. Trager (16) later reported that the larvae of the mosquito, Aedes aegypti, require biotin in their medium; hokeyer, oleic acid and the lipides of plasma possess biotin-sparing activity for this organism. Several studies have demonstrated that simple replacement of biotin by fatty acids has not occurred, since powerful biotin inhibitors in the experiment reported have not prevented the growth of organisms in which biotin has been replaced by aspartic acid and certain lipides (17-19). The present investigation was undertaken to determine the relative biotin-like activity of the positional isomers and stereoisomers of oleic acid