Diacetyl (Acetoin) Reductase from Aerobacter aerogenes

The native and subunit molecular weights of diacetyl (acetoin) reductase from Aerobacter aerogenes have been investigated by sedimentation equilibrium analysis and gel electrophoresis. The values obtained are 100000 for the native enzyme and 25000 for the subunit. The native enzyme is dissociated into four equal‐sized subunits by exposure to guanidine hydrochloride, urea, or dodecylsulfate. The subunits can reassociate in the presence of bovine serum albumin to yield the native enzyme. Electron micrographs of enzyme molecules, negatively stained, show that they appear primarily as tetramers with four subunits at the corners of squares. The molecular weight as calculated from the diameter of the subunits is consistent with the values obtained by sedimentation equilibrium and gel electrophoresis.