| Abstract: | 1-Aminocyclopropane-1-carboxylic acid (ACC), which is a precursor of ethylene in plants, has never been known to occur in microorganisms. We describe the synthesis of ACC by Penicillium citrinum, purification of ACC synthase EC 4.4.1.14] and ACC deaminase EC 4.1.99.4], and their properties. Analyses of P. citrinum culture showed occurrence of ACC in the culture broth and in the cell extract. ACC synthase was purified from cells grown in a medium containing 0.05% L-methionine and ACC deaminase was done from cells incubated in a medium containing 1% 2-aminoisobutyrate. The purified ACC synthase, with a specific activity of 327 milliunit/mg protein, showed a single band of M r 48,000 in SDS-polyacrylamide gel electrophoresis. The molecular mass of the native enzyme by gel filtration was 96,000 Da. The ACC synthase had the K m for S-adenosyl-L-methionine of 1.74 mM and k cat of 0.56 s-1 per monomer. The purified ACC deaminase, with a specific activity of 4.7 unit/mg protein, showed one band in SDS-polyacrylamide gel electrophoresis of M r 41,000. The molecular mass of the native ACC deaminase was 68,000 Da by gel filtration. The enzyme had a K m for ACC of 4.8 mM and k cat of 3.52 s-1. The presence of 7 mM Cu2+ in alkaline buffer solution was effective for increasing the stability of the ACC deaminase in the process of purification. |
