No abstract

Hen liver preparations which desaturate stearic acid at the 9,10 position to form oleic acid have been found to desaturate other saturated fatty acids of carbon chain length from 12 to 20 and 22. The 9,10‐monoenoic fatty acid of the same chain length as the substrate fatty acid is the major product formed. Minor amounts of the 10,11‐ and 11, 12‐monoenoic acids are also formed. Maximum desaturation occurred with the C14 fatty acid substrate and with the fatty acids C17 and C18, suggesting the presence of at least two desaturating systems. The cyclopropene fatty acids, sterculic and malvalic acids, inhibited the desaturation of all thefatty acids at the 9,10 position but desaturation at the 10,11 and 11, 12 positions was affected only slightly. The effect is not due to inhibition of the primary activating enzyme, the long chain acyl CoA synthetase. Sterculic acid is a more effective inhibitor than either malvalic acid or sterculyl alcohol, probably because these cyclopropene compounds do not block the desaturating site of the enzyme as completely as sterculic acid.

233When Tween 80 (polyoxyethylene sorbitan mono-oleate) was given as a supplement in basal ammonium sulphate/glucose medium to the yeast Trigonopsis variabilis, it induced the development, throughout growth, of populations consisting almost entirely of triangular cells. This induction was inhibited by an increase in growth temperature and by adding specific concentrations of short-chain alcohols to the medium. Only Tween 80 among the Tween detergents and Span 80 (sorbitan mono-oleate) among the Span detergents induced the formation of triangular cells, and Brij 96 (polyoxyethylene-10-oleyl ether) and sodium oleate were ineffective. These results indicate that the ester-linked sorbitan oleate is the chemical characteristic which is responsible for the effect of Tween on the morphology of T. variabilis, in a system more reproducible than any other previously investigated.