Catalyzes the production of hydrogen sulfide (H2S) from cysteine. Is mainly responsible for the degradation of cysteine to generate H2S, a regulator of stomatal movement and closure. Has high affinity for D-cysteine. Possesses 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Acts as a regulator of ACC levels and causes changes in ethylene levels. D-cysteine + H2O = H(+) + hydrogen sulfide + NH4(+) + pyruvate 1-aminocyclopropane-1-carboxylate + H2O = 2-oxobutanoate + NH4(+) kcat is 6 sec(-1) for D-cysteine as substrate. Optimum pH is 8.0. Highly expressed in stems and cauline leaves, and at lower levels in roots, rosette leaves and flowers. By drought. Produced by alternative initiation at Met-20 of isoform 1. Belongs to the ACC deaminase/D-cysteine desulfhydrase family. Truncated N-terminus.