Inactivation of soybean sterol 24-C-methyltransferase by elongated sterol side chains at C26.

The enzymatic C-methylation reaction catalyzed by the Glycine max sterol 24-C-methyltransferase was studied with substrate analogs containing a cycloartenol nucleus (CA) and a double bond (8) or triple bond (14) attached to C26. The production of the corresponding C24(28)-methylene olefin and time-dependent inhibition kinetics of k(inact) 0.24 min(-1) (CA-8) or 0.06 min(-1) (CA-14) indicates an active-site directed process and partitioning to produce novel products.