Synthesis and Degradation of 1-Aminocyclopropane-1-carboxylic Acid by Penicillium citrinum

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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 0.56s^-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 3.52s^-1. The presence of 7mM Cu^2+ in alkaline buffer solution was effective for increasing the stability of the ACC deaminase in the process of purification.
社団法人日本農芸化学会の論文
1999-03-23