S-Adenosyl-l-methionine–cycloartenol methyltransferase activity in cell-free systems from Trebouxia sp. and Scenedesmus obliquus

Abstract

1. Homogenates prepared from Trebouxia sp. 213/3 and Scenedesmus obliquus exhibited S-adenosyl-l-methionine–cycloartenol methyltransferase activity. 2. The products of the reaction, with cycloartenol as the substrate, were 24-methylenecycloartanol and cyclolaudenol. 3. Optimal enzyme activity was found in homogenates prepared at pH7.6 and the transmethylase was distributed between the supernatant and microsomal fractions of the Trebouxia homogenate. 4. The relevance of these results is discussed in relation to C28 and C29 sterol production in the algae.