The positional specificity of a desaturase in the psychrophilic bacterium Micrococcus cryophilus (ATCC 15174).

The positional specificity of the desaturase activity in the psychrophilic bacterium Micrococcus cryophilus (ATCC 15174) is shown to be delta9. The desaturase is inhibited by sterculic acid. Small amounts of delta8, delta10 and delta11 isomers are present. The implications of these findings for fatty acid metabolism in M. cryophilus are discussed. It is suggested that the temperature-dependent chain length change, known to occur in the phospholipid fatty acids of this bacterium, is not mediated by either a temperature-dependent change in desaturase substrate specificity or the induction of new desaturase enzymes with novel positional specificity. It is concluded that the control by temperature of fatty acid chain length is mediated by either a temperature-dependent change in the products of fatty acid synthetase or a temperature-sensitive palmitate elongase.