Measurement of Serine Acetyltransferase Activity in Crude Plant Extracts by a Coupled Assay System Using Cysteine Synthase

Abstract
Serine acetyltransferase (SATase) (EC 2.3.1.30) catalyzes the formation of Oacetyl-L-serine (OAS) from L-serine in the presence of acetyl-CoA. A novel assay method was developed for measuring this enzyme activity in extracts from plant tissues. The assay consists of a coupled system in which the OAS formed is converted to cysteine by the addition of cysteine synthase (CSase) (EC 4.2.99.8). Cysteine thus formed is determined colorimetrically and serves as a measure for SATase activity. This method is rapid, simple and sensitive, and can be readily adapted for measurement of SATase activity in crude tissue extracts or homogenates.