Synthesis and degradation of 1-aminocyclopropane-1-carboxylic acid by Penicillium citrinum

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 ACG deaminase IEC 4.1.99.4], and their properties, Analyses of II. 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 AGC 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 at 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 ACG 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 lace 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 Bead 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.