Elsevier

Description

Serine acetyltransferase (SAT; EC 2.3.1.30) catalyzes the CoA-dependent acetylation of the side chain hydroxyl group of l-serine to form O-acetyl serine, in the first step of the l-cysteine biosynthetic pathway. Since this pathway is selectively present in a few parasitic protists and absent in mammals, it represents a reasonable target to develop new chemotherapeutics. Entamoeba histolytica apparently possesses three SAT isotypes (EhSAT1-3) showing 48–73% mutual identity, a calculated molecular mass of 34.4–37.7kDa, and an isoelectric point of 5.70–6.63. To better understand the role of individual SAT isotypes, we determined kinetic and inhibitory parameters of recombinant SAT isotypes. While the three SAT isotypes showed comparable Km and kcat for l-serine and acetyl-CoA, they showed remarkable differences in their sensitivity to inhibition by l-cysteine. The Ki values for l-cysteine varied by 100-fold (4.7 …