May catalyze the production of hydrogen sulfide (H2S) from cysteine. Interacts in vitro with QS (PubMed:18978034). Belongs to the class-V pyridoxal-phosphate-dependent aminotransferase family. Identified as a putative plastidic SufS-like protein and thus called CpNifS3 (PubMed:18978034). However, it seems to be more related to L-cysteine desulfhydrase.