Acts as a cysteine synthase. Plays a role in the sulfide detoxification in mitochondria. hydrogen sulfide + O-acetyl-L-serine = acetate + L-cysteine Amino-acid biosynthesis; L-cysteine biosynthesis; L-cysteine from L-serine: step 2/2. Homodimer (By similarity). Interacts with SAT3. Component of the cysteine synthase complex (CSC) composed of two OAS-TL dimers and one SAT hexamer. A number of isoforms are produced. According to EST sequences. No visible phenotype but displays lower levels of thiols in roots (PubMed:18024555). Growth retardation (PubMed:18223034). Defects in root hair formation (PubMed:22511607). Belongs to the cysteine synthase/cystathionine beta-synthase family.