Ranjan Bibhuti, Singh Bijender, Satyanarayana T
Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India.
Department of Microbiology, M.D. University, Rohtak, Haryana, 124001, India.
Appl Biochem Biotechnol. 2015 Dec;177(8):1753-66. doi: 10.1007/s12010-015-1851-4. Epub 2015 Oct 3.
Sporotrichum thermophile produces very low titres of phytase (St-Phy) extracellularly, which is acidstable, thermostable, and protease insensitive with broad substrate specificity, and therefore, the gene encoding phytase (St-Phy) has been cloned and expressed in E. coli. The purified recombinant phytase (rSt-Phy) has the molecular mass of 55 kDa with Km and Vmax (calcium phytate), kcat and kcat/Km of 0.143 mM, 185.05 nmoles mg(-1) s(-1), 5.1 × 10(3) s(-1), and 3.5 × 10(7) M(-1) s(-1), respectively. Mg(2+) and Ba(2+) display slight stimulatory effect on the enzyme, while it is inhibited by other ions to a varied extent. The enzyme is also inhibited by chaotropic agents (guanidinium hydrochloride, potassium iodide, and urea), Woodward's reagent K, and 2,3-butanedione but resistant to both pepsin and trypsin. The rSt-Phy is useful in dephytinization of tandoori and naan (unleavened flat Indian breads), and bread, liberating soluble inorganic phosphate that mitigates anti-nutrient effects of phytic acid.
嗜热侧孢霉在细胞外产生的植酸酶（St-Phy）活性很低，该酶具有酸稳定性、热稳定性，对蛋白酶不敏感，底物特异性广，因此，编码植酸酶的基因（St-Phy）已被克隆，并在大肠杆菌中表达。纯化后的重组植酸酶（rSt-Phy）分子量为55 kDa，其与肌醇六磷酸钙的Km和Vmax、kcat以及kcat/Km分别为0.143 mM、185.05 nmol mg⁻¹ s⁻¹、5.1×10³ s⁻¹和3.5×10⁷ M⁻¹ s⁻¹。Mg²⁺和Ba²⁺对该酶有轻微的刺激作用，而其他离子则在不同程度上对其产生抑制。该酶还受到离液剂（盐酸胍、碘化钾和尿素）、伍德沃德试剂K和2,3-丁二酮的抑制，但对胃蛋白酶和胰蛋白酶均具有抗性。rSt-Phy可用于印度烤饼和馕（未发酵的印度扁面包）以及面包的脱植酸处理，释放出可溶性无机磷酸盐，减轻植酸的抗营养作用。
