PARTIAL-PURIFICATION AND CHARACTERIZATION OF 1-AMINOCYCLOPROPANE-1-CARBOXYLATE DEAMINASE FROM THE PLANT-GROWTH PROMOTING RHIZOBACTERIUM PSEUDOMONAS-PUTIDA GR12-2

The plant growth promoting rhizobacterium Pseudomonas putida GR12-2 can utilize 1-aminocyclopropane-1-carboxylate (ACC) as a sole nitrogen source because it possess the unusual enzyme ACC deaminase, which hydrolyzes ACC to ammonia and alpha-ketobutyrate. This enzyme, which is thought to be intimately involved in the mechanism that the bacterium uses to promote root elongation in developing canola seedlings, was partially purified and characterized. The native form of the enzyme is a trimer with a molecular mass of 105 kDa and a subunit molecular mass of 35 kDa. ACC deaminase activity is found in the cytoplasm of the bacterium, is induced by low levels (i.e., 100 nM) of ACC, and has a temperature optimum at approximately 30 degrees C and a pH optimum of 8.5. These properties are very similar to those reported for ACC deaminase from another soil bacterium, Pseudomonas sp. strain APC.