Fatty-acid synthesis in lactating-goat mammary gland. 2. Medium-chain fatty acid synthesis

Addition of goat, rat, rabbit and cow mammary microsomal fraction to fatty acid synthetase of goat mammary gland induced C10 fatty acid synthesis. When the microsomal fractions from rat, rabbit and cow mammary gland were incubated with their respective fatty acid synthetases only the cow enzyme synthesized significant amounts of C10 compared to the purified fatty acid synthetases alone. The goat mammary microsomal fraction was not able to induce C10 synthesis by rat and rabbit mammary-gland fatty acid synthetase, but only by the goat and cow enzyme. Both goat and cow mammary-gland fatty acid synthetase have in contrast to the rabbit and rat enzymes the ability to hydrolyse medium-chain acyl-thioesters. We therefore suggest a novel mechanism for medium-chain fatty acid synthesis in lactating-goat mammary gland. This mechanism involves an activation of the medium-chain acyl-thioester hydrolase within the fatty acid synthetase of goat mammary gland by an unknown microsomal factor.