β-Cyanoalanine synthase (CAS; EC 4.4.1,9) and two kinds of cysteine synthases (CS; EC 220.127.116.11) have been purified from the particulate fraction of potato tubers. By DEAE Sephacel and Resource PHE chromatography, CAS activity was separated from two CS activities, designated as CS-1 and CS-2. The molecular masses of CAS, CS-1 and CS-2 were estimated to he 37, 39 and 34 kDa, respectively, by SDS-PAGE analysis. The purified CAS had CS activity, and both CS-1 and CS-2 had CAS activity. However, CAS and CSs had significant differences in kinetic characters. The antibody raised against purified CAS discriminated CAS from CSs, whereas the antibody raised against purified CS-2 recognized CS-1 and CS-2 but not CAS. The molecular mass and the partial amino acid sequence of CS-2 were similar to those of the cytosolic CS of potato, whereas the molecular mass of CS-1 was similar to that of the plastidic CS. The partial amino acid sequence of CAS was similar to those of CS isozymes, especially the mitochondrial CS isolated from spinach.
All Science Journal Classification (ASJC) codes
- Plant Science
- Cell Biology