title: Purification and properties of S-alkyl-L-cysteine lyase from seedlings of Acacia farnesiana Willd.
abstract: 1. An S-alkyl-L-cysteine lyase (EC 4.4.1.6) was purified to apparent homogeneity from extracts of acetone-dried powders of the hypocotyls of etiolated 5-day-old seedlings of Acacia farnesiana Willd. 2. The enzyme catalyses a beta-elimination reaction and will utilize both the thioether and sulphoxide form of the substrate. 3. There is a braod specificity with regard to the alkyl substituent, but cystathionine is utilized very poorly. 4. The pH optimum is 7.8 and the Km value for the probable natural substrate L-djenkolate is 0.3 mM. 5. Both sodium dodecyl sulphate-polyacrylamide-gel electrophoresis and ultracentirfugal analysis give a molecular weight of about 144000. 6. One mol of pyridoxal phosphate is bound/mol of enzyme. 7. The energy of activation with L-djenkolate as the substrate is 53.1 kJ/mol. 8. The enzyme has a partial specific volume of 0.56 and S20,w 7.26S.
mesh_terms: D000045:Acacia / Q000201:enzymology*; D000596:Amino Acids / Q000032:analysis; D003545:Cysteine; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008190:Lyases / Q000302:isolation & purification* / Q000378:metabolism; D008970:Molecular Weight; D011732:Pyridoxal Phosphate / Q000378:metabolism
chemical_list: D000596:Amino Acids; D011732:Pyridoxal Phosphate; D008190:Lyases; D003545:Cysteine