The C-S lyases of higher plants. Purification and characterization of homogeneous alliin lyase of leek (Allium porrum)

The characteristic odors of freshly macerated tissue of Allium species such as garlic and onion are due to the action of the enzyme alliin lyase (EC 4.4.1.4) on endogenous S-alkyl-I-cysteine sulfoxides which are present as secondary amino acids yielding volatile sulfur-containing products. Purification and characterization of the alliin lyase of leek ( Allium porrum L.) has been carried out for comparison with the analogous enzymes previously characterized from garlic and onion. The purification involved homogenization, followed by ammonium sulfate fractionation, elution from an hydroxylapatite column, concentration of the active fractions and passage through a concanavalin A-Sepharose 4B affinity column. The purified enzyme was found to be a glycoprotein with a pH optimum for activity of 8.0. Sodium dodecylsulfate-urea polyacrylamide gel electrophoresis gels of the homogeneous leek enzyme showed it consisted of 1 subunit with a molecular weight of 48000. By gel filtration, 2 stable forms of the native enzyme with molecular weights of 386000 and 580000 were found.