title: Beta-cyanoalanine synthase: purification and characterization.
abstract: Beta-cyano-L-alanine synthase [L-cysteine hydrogen-sulfide-lyase (adding HCN), EC 4.4.1.9] was purified about 4000-fold from blue lupine seedlings. The enzyme was homoegeneous on gel electrophoresis and free of contamination by other pyridoxal-P-dependent lyases. The enzyme has a molecular weight of 52,000 and contains 1 mole of pyridoxal-P per mole of protein; its isoelectric point is situated at pH 4.7. Its absorption spectrum has two maxima, at 280 and 410 nm. L-Cysteine is the natural primary (amino acid) substrate; beta-chloro- and beta-thiocyano can serve (with considerably lower affinity) instead of cyanide as cosubstrates for cyanoalanine synthase. The synthase is refractory to DL-cycloserine and D-penicillamine, potent inhibitors of many pyridoxal-P-dependent enzymes. Cyanoalanine synthase catalyzes slow isotopic alpha-H exchange in cysteine and in end-product amino acids; the rates of alpha-H exchange in nonreacted (excess) cysteine are markedly increased in the presence of an adequate cosubstrate; no exchange is observed of H atoms in beta-position.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000625:Aminooxyacetic Acid / Q000494:pharmacology; D013437:Carbon-Sulfur Lyases / Q000302:isolation & purification* / Q000378:metabolism; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003486:Cyanides; D003523:Cycloserine / Q000494:pharmacology; D003545:Cysteine; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D007700:Kinetics; D008190:Lyases / Q000302:isolation & purification*; D008970:Molecular Weight; D010396:Penicillamine / Q000494:pharmacology; D010944:Plants / Q000201:enzymology*; D011422:Propionates / Q000494:pharmacology; D011732:Pyridoxal Phosphate / Q000032:analysis; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors
chemical_list: D000596:Amino Acids; D003486:Cyanides; D011422:Propionates; D000625:Aminooxyacetic Acid; D011732:Pyridoxal Phosphate; D003523:Cycloserine; D008190:Lyases; D013437:Carbon-Sulfur Lyases; C019955:beta-cyanoalanine synthase; D010396:Penicillamine; D003545:Cysteine