Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South Street, Beijing 100081, People's Republic of China.
Appl Microbiol Biotechnol. 2011 Oct;92(2):317-25. doi: 10.1007/s00253-011-3309-0. Epub 2011 May 12.
A phytase-encoding gene (phyA115) was cloned from Janthinobacterium sp. TN115, a symbiotic bacterial strain isolated from the gut contents of Batocera horsfieldi larvae (Coleoptera: Cerambycidae), and expressed in Escherichia coli. The 1,884-bp full-length gene encodes a 28-residue putative signal peptide and a 599-residue mature protein with a calculated mass of 64 kDa. The deduced PhyA115 shares low identity with known sequences (47% at most) and contains an N-terminal incomplete domain (residues 29-297; domain N) and a typical β-propeller phytase domain at the C terminus (residues 298-627; domain C). Distinct from other β-propeller phytases that have neutral pH optima (pH 6.0-7.5), purified recombinant PhyA115 exhibits maximal activity at pH 8.5 and 45°C in the presence of 1 mM Ca(2+) and is highly active over a wider pH range (pH 6.0-9.0). These results indicate that PhyA115 is a β-propeller phytase that has application potential in aquaculture feed. To our knowledge, this is the first report of cloning of a phytase gene from the symbiotic microbes of an insect digestive tract and from the genus Janthinobacterium. The N-terminal incomplete domain is found to have no phytase activity but can influence the pH property of PhyA115.
从共生细菌 Janthinobacterium sp. TN115 中克隆了植酸酶编码基因（phyA115），该共生细菌是从幼虫肠道内容物中分离出的一种共生细菌Batocera horsfieldi（鞘翅目：天牛科），并在大肠杆菌中表达。全长 1884bp 的基因编码一个 28 个残基的假定信号肽和一个 599 个残基的成熟蛋白，计算分子量为 64kDa。推断的 PhyA115 与已知序列的同源性较低（最高 47%），并且包含 N 端不完全结构域（残基 29-297；结构域 N）和 C 端典型的β-旋转植酸酶结构域（残基 298-627；结构域 C）。与其他具有中性 pH 最佳值（pH 6.0-7.5）的β-旋转植酸酶不同，纯化的重组 PhyA115 在 1mM Ca(2+)存在下，在 pH 8.5 和 45°C 下表现出最大活性，并且在更宽的 pH 范围内具有很高的活性（pH 6.0-9.0）。这些结果表明 PhyA115 是一种β-旋转植酸酶，在水产养殖饲料中有应用潜力。据我们所知，这是首次从昆虫消化道共生微生物和 Janthinobacterium 属中克隆植酸酶基因的报道。发现 N 端不完全结构域没有植酸酶活性，但可以影响 PhyA115 的 pH 特性。
