A gene (estA', 804 bp) from Streptomyces lividans TK24 was artificially synthesized and successfully overexpressed as a 6His-tagged fusion protein in Escherichia coli. It encoded a carboxylesterase (EstA) that composed of 267 amino acids with a predicted molecular weight of 28.56 kDa. Multiple sequence alignment indicated that EstA has typical characteristics of esterases, including a catalytic triad (Ser93-Asp194-His224) and a conserved pentapeptide motif (Gly91-Leu92-Ser93-Met94-Gly95). Simultaneously, phylogenetic analysis indicated that EstA belongs to family VI. Biochemical characterization displayed its optimum enzyme activity was at 55 ℃ and pH 8.5. Additionally, EstA exhibited higher activity towards short carbon substrates and showed the outstanding catalytic efficiency for pNPA2 with k_cat/K_m of 2296.14 ± 10.35 s⁻¹ mM⁻¹. Notably, EstA has hyper-thermostability and good alkali stability. The activity of EstA did not change obviously when incubated at 50 and 100 ℃ for 337 and 1 h, independently. Besides, by incubating at 100 ℃ for 6 h, EstA remained about half of its initial activity. Moreover, EstA showed stability at pH ranging from 8.0 to 11.0, and about 90% residual enzyme activity was reserved by being treated at pH 8.0 or 9.0 for 80 h, especially. Such multiple features prepare EstA for a potential candidate in the field of biological catalysis of some industrial applications under harsh conditions.

人工合成了来自青霉链霉菌TK24的基因（estA'，804 bp），并成功地在大肠杆菌中过表达为6His标记的融合蛋白。。它编码了一个由267个氨基酸组成的羧酸酯酶（EstA），预测分子量为28.56 kDa。多个序列比对表明EstA具有酯酶的典型特征，包括催化三联体（Ser93-Asp194-His224）和保守的五肽基序（Gly91-Leu92-Ser93-Met94-Gly95）。同时，系统发育分析表明EstA属于VI族。生化特征表明其最佳酶活性为55℃和pH 8.5。另外，EstA对短碳底物表现出更高的活性，并显示出对p NPA2的出色催化效率，k _cat / K _m为2296.14±10.35 s ^-1  mM ^-1。值得注意的是，EstA具有超热稳定性和良好的碱稳定性。分别在50和100℃下孵育337和1小时，EstA的活性没有明显改变。此外，通过在100℃下孵育6小时，EstA仍保持了其初始活性的一半左右。此外，EstA在8.0至11.0的pH范围内表现出稳定性，特别是在pH 8.0或9.0下处理80小时可保留约90％的残留酶活性。这样的多种功能使EstA成为在苛刻条件下某些工业应用的生物催化领域的潜在候选者。