Basic analysis and development of novel lactonases promising for industrial catalysts

微生物内酯酶（内酯环裂解酶）具有独特的性质，尖孢镰刀菌（Fusarium oxysporum）的内酯环裂解酶催化醛糖酸内酯和D-泛内酯（D-PL）的可逆和立体专一性水解，可用于外消旋PL的光学拆分。根癌农杆菌酶能水解多种芳香内酯，并与镰刀菌酶一样催化PL的立体专一性水解，但其选择性相反。乙酸钙不动杆菌（Acinetobacter calcoaceticus）催化二氢香豆素特异性水解的酶属于丝氨酸-酶家族，可用于DL-β-乙酰硫代异丁酸甲酯的对映选择性水解和西曲酸甲酯的区域选择性水解。该酶在H_2O_2和二氢香豆素作用下也能催化一氯敌酮的溴化反应。研究了醋酸钙。从A.醋酸钙催化氧化 ...更多信息 过氧乙酸的降解与时间和环境有关。基因（dch）是从细菌的染色体DNA克隆的。dch的开放阅读框长831 bp，编码272个氨基酸，推导的氨基酸序列与细菌丝氨酸酯酶和血红素卤代过氧化物酶的氨基酸序列高度相似。dch基因在A.醋酸钙菌基因组dch破坏菌对过氧乙酸的生长抑制作用比亲株敏感。另一方面，重组E.表达DCH的大肠杆菌细胞对过氧乙酸的抗性更强。推定的过氧化氢酶基因被发现直接下游的dch，和Nostrum杂交分析表明，它们都是转录的一部分，多顺反子mRNA。这些结果表明，二氢香豆素水解酶在体内解毒过氧酸与过氧化氢酶，即首先，过氧酸被水解成相应的酸和过氧化氢，然后产生的过氧化氢被过氧化氢酶降解。少

Microbial lactonases (lactone-ring-cleaving enzymes) with unique characteristics were found. The Fusarium oxysporum enzyme catalyzes the reversible and stereospecific hydrolysis of aldonate lactones and D-pantolactone (D-PL), and is useful for the optical resolution of racemic PL. The Agrobacterium tumefaciens enzyme hydrolyzes several aromatic lactones, and catalyzes the stereospecific hydrolysis of PL like the Fusarium enzyme, but its selectivity is opposite. The Acinetobacter calcoaceticus enzyme catalyzing the specific hydrolysis of dihydrocoumarin belongs to serine-enzyme family, and is useful for enantioselective hydrolysis of methyl DL-β-acetylthioisobutyrate and regioselective hydrolysis of methyl cetraxate. This enzyme also catalyzes the bromination of monochlorodimedon when incubated with H_2O_2 and dihydrocoumarin.The physiological role of a bifunctional enzyme, dihydrocoumarin hydrolase of A. calcoaceticus was investigated. Purified enzyme from A. calcoaceticus catalyzed do … More se- and time-dependent degradation of peracetic acid. The gene (dch) was cloned from the chromosomal DNA of the bacterium. The open reading frame of dch was 831 bp long, corresponding to a protein of 272 amino acid residues, and deduced amino acid sequence showed high similarity to those of bacterial serine-esterases and noheme haloperoxidases. The dch gene was disrupted by homologous recombination on the A. calcoaceticus genome. The dch disruptant strain was more sensitive to growth inhibition by peracetic acid than the parent strain. On the other hand, recombinant E. coli cells expressing dch were more resistant to peracetic acid. The putative catalase gene was found immediately downstream of dch, and Nothern hybridization analysis revealed that both of them were transcript as part of a polycistronic mRNA. These results suggested that dihydrocoumarin hydrolase in vivo detoxified peroxoacids in conjunction with the catalase, i.e. at first, peroxoacids are hydrolyzed to the corresponding acids and hydrogen peroxide by dihydrocoumarin hydrolase, and then the resulting hydrogen peroxide is degraded by the catalase. Less