Acts as a major cysteine synthase, probably involved in maintaining organic sulfur level. hydrogen sulfide + O-acetyl-L-serine = acetate + L-cysteine Interaction with the sulfate transporter SULTR1;2 enhances its catalytic activity. Amino-acid biosynthesis; L-cysteine biosynthesis; L-cysteine from L-serine: step 2/2. Homodimer. Interacts with SAT1. Component of the cysteine synthase complex (CSC) composed of two OAS-TL dimers and one SAT hexamer. Interacts with SULTR1;2. No visible phenotype but displays lower levels of thiols in roots and leaves, and also an affected sulfur balance. Also shows an increased sensitivity to cadmium stress. Belongs to the cysteine synthase/cystathionine beta-synthase family.