Solubilization, Purification, and Properties of Membrane-BoundD-Glucono-δ-lactone Hydrolase fromGluconobacter oxydans

Membrane-bound glucono-delta-lactonase (MGL) was purified to homogeneity from the membrane fraction of Gluconobacter oxydans IFO 3244. After solubilization with 1 M CaCl2, MGL was purified in the presence of Ca2+ and detergent. A single band corresponding to 60 kDa appeared in SDS-PAGE. The molecular weight of MGL was judged to be 120 k. Differently from cytoplasmic lactonases, MGL showed optimum pH in an acidic range of 5-5.5. It was highly sensitive to metal-chelating agents such as EDTA, and the lost MGL activity was restored to the original level by the addition of divalent cations such as Ca2+ or Mg2+. The purified MGL was strictly dependent on Ca2+ and underwent rapid denaturing precipitation on Ca2+ depletion even in the presence of detergent. This communication can be the first one dealing with the solubilization, purification and properties of MGL.