InterPro domain: IPR031111

Cyanide is produced in higher plants during ethylene biosynthesis and needs to be removed from plant tissues to avoid toxicity. L-3-cyanoalanine synthase or beta-cyanoalanine synthase (CAS) catalyses the conversion of cyanide and cysteine to beta-cyanoalanine and sulfide [ 1 ], and then beta-cyanoalanine is converted into asparagine by beta-cyanoalanine hydrolyase. Ethylene is an essential hormone for ripening and expression of CAS is induced during fruit ripening [ 2 ]. CAS shows homology with Cys synthase (CS) and exhibits detectable CS activity. Both CAS and CS belong to the same enzyme family, the beta-substituted Ala synthases [ 3 ]. CAS is localised in the mitochondria [ 4 ].

1. Beta-cyanoalanine synthase and cysteine synthase from potato: molecular cloning, biochemical characterization, and spatial and hormonal regulation. Plant Mol. Biol. 46, 749-60
2. Expression of MdCAS1 and MdCAS2, encoding apple beta-cyanoalanine synthase homologs, is concomitantly induced during ripening and implicates MdCASs in the possible role of the cyanide detoxification in Fuji apple (Malus domestica Borkh.) fruits. Plant Cell Rep. 26, 1321-31
3. Cytosolic beta-cyanoalanine synthase activity attributed to cysteine synthases in cocklebur seeds. Purification and characterization of cytosolic cysteine synthases. Plant Cell Physiol. 39, 671-80
4. beta-Cyanoalanine synthase is a mitochondrial cysteine synthase-like protein in spinach and Arabidopsis. Plant Physiol. 123, 1163-71