THE Joc~s.4~ OF BIOLOGICAL CHENISTRY

A membrane-bound oleyl coenzyme A desaturase from maturing Carthumus tinctorius seeds specifically catalyzed the conversion of oleyl-CoA to linoleyl-CoA. Any modification of the substrate, that is, a trans double bond, a shift in the position of the cis double bond, chain length, and the substitution of acyl carrier protein for CoA as the thioester moiety resulted in complete loss of activity. The system was strongly inhibited by a number of -SH reagents and metal chelators; carbon monoxide at various concentrations was ineffective ; cyanide partially inhibited. Although DPNH and molecular oxygen were components of the system, DPNH could be replaced by photochemically reduced ferredoxin. This result would suggest that DPNH did not interact directly with molecular oxygen and the desaturase but served only as a source of electror_s. Attempts at solubilization were unsuccessful.