Abstract
Serine acetyltransferase (SATase) catalyzes the formation of O-acetyl-L-serine (OAS) which is the essential precursor of cysteine biosynthesis. There are five SATase isozyme genes on Arabidopsis genome. Among these, SAT-c, SAT-p, and SAT-m were characterized by differences of subcellular localization and the sensitivity to the feedback inhibition by cysteine. By the analyses of enzymatic properties using recombinant proteins of SAT106 and SAT#5, both of these enzymes synthesized OAS from acetyl-CoA and serine, although the affinities of these enzymes for their substrates were very low. Both of SAT106 and SAT#5 seem to be localized in cytosol. The activity of SAT#5 was feedback-inhibited by cysteine, whereas SAT106 was not subjected to this feedback inhibition. To reveal the role of each SATase isozymes, we are currently dealing with the expression analysis of each SATases under various stress conditions and the analysis of the knock-out mutant plant of each SATases.
