Purification and properties of the alpha-acetolactate decarboxylase from Lactococcus lactis subsp. lactis NCDO 2118.

alpha-Acetolactate decarboxylase from Lactococcus lactis subsp. lactis NCDO 2118 was expressed at low levels in cell extracts and was also unstable. The purification was carried out from E. coli in which the enzyme was expressed 36-fold higher. The specific activity was 24-fold enhanced after purification. The main characteristics of alpha-acetolactate decarboxylase were: (i) activation by the three branched chain amino acids leucine, valine and isoleucine; (ii) allosteric properties displayed in absence and Michaelis kinetics in the presence of leucine. The enzyme is composed of six identical subunits of 26,500 Da.