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Cloning and characterization of a novel amidase from <Emphasis Type="Italic">Paracoccus</Emphasis> sp. M-1, showing aryl acylamidase and acyl transferase activities
Authors:Weiliang?Shen  Honghong?Chen  Kaizhi?Jia  Jun?Ni  Email author" target="_blank">Xin?YanEmail author  Shunpeng?Li
Institution:(1) Key Laboratory of Microbiological Engineering of Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, 6 Tongwei Road, Nanjing, Jiangsu, 210095, People’s Republic of China;
Abstract:A novel amidase gene, designated pamh, was cloned from Paracoccus sp. M-1. Site-directed mutagenesis and bioinformatic analysis showed that the PamH protein belonged to the amidase signature enzyme family. PamH was expressed in Escherichia coli, purified, and characterized. The molecular mass of PamH was determined to be 52 kDa with an isoelectric point of 5.13. PamH displayed its highest enzymatic activity at 45°C and at pH 8.0 and was stable within a pH range of 5.0–10.0. The PamH enzyme exhibited amidase activity, aryl acylamidase activity, and acyl transferase activity, allowing it to function across a very broad substrate spectrum. PamH was highly active on aromatic and short-chain aliphatic amides (benzamide and propionamide), moderately active on amino acid amides, and possessed weak urease activity. Of the anilides examined, only propanil was a good substrate for PamH. For propanil, the k cat and K m were 2.8 s?1 and 158 μM, respectively, and the catalytic efficiency value (k cat/K m) was 0.018 μM?1 s?1. In addition, PamH was able to catalyze the acyl transfer reaction to hydroxylamine for both amide and anilide substrates, including acetamide, propanil, and 4-nitroacetanilide; the highest reaction rate was shown with isobutyramide. These characteristics make PamH an excellent candidate for environmental remediation and an important enzyme for the biosynthesis of novel amides.
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