SELECTIVE USE OF L-VALINE AND L-ISOLEUCINE FOR THE BIOSYNTHESIS OF BRANCHED-CHAIN FATTY-ACIDS IN RAT SKIN

Iso- and anteiso-fatty acids are detected in more than trace amounts i n rat skin surface lipid, The terminal portion of even carbon number i so- and anteiso-fatty acids are synthesized respectively from valine ( Val) and isoleucine (Ile) by essentially the same reaction sequences e stablished for straight chain fatty acids, This paper describes the st ereospecific biosynthesis of these branched chain fatty acids (BCFAs) and alcohols (BCFALs) in rat skin, Dependence of the concentration of these BCFAs on dietary L-Val and L-Ile was studied, Concentrations of even carbon number iso- and anteiso-fatty acid increased respectively with dietary L-Val and L-Ile, The saturation dose appeared to be 2% fo r L-Val and 1% for L-ne. Supplementation of the diet with 2% D-Val, ho wever, did not affect the concentration of even carbon number iso-fatt y acid in rat skin surface lipid despite a comparable serum Val level to that of the 2% L-Val group, A similar experiment using 1% DL-Ile fo und that L-isomer, but not D-isomer, in the circulation was used for t he biosynthesis of anteiso-fatty acids. This view was applicable to th e incorporation of D-Val and DL-Ile into related BCFALs.