Purification and Characterization of Monomeric Lysine Decarboxylase from Soybean (Glycine max) Axes

Lysine decarboxylase (EC 4.1.1.18) was purified 364-fold from 2-day-old soybean (Glycine max) axes. The enzyme was a monomeric protein having a molecular mass of 95,000 Da and an isoelectric point of 4.0. TheKmforl-lysine was 1.17 mM. The optimal temperature and pH of the enzyme were 37°C and 7.5, respectively. Storage of the enzyme at temperatures ranging from 0 to 4°C caused a 50% loss of the activity in 24 h. The enzyme was competitively inhibited by Cl−with aKivalue of 1.46 mM. However, the activity of the purified enzyme was not inhibited by F−, Br−, I−, H2PO−4, HPO2−4, or SO2−4. Cadaverine at 1 mM inhibited the enzyme activity by 35%.