Szczyrba Elżbieta, Greń Izabela, Bartelmus Grażyna
Institute of Chemical Engineering, Polish Academy of Sciences, Bałtycka 5, 44-100, Gliwice, Poland.
Folia Microbiol (Praha). 2014 Mar;59(2):99-105. doi: 10.1007/s12223-013-0268-0. Epub 2013 Aug 3.
Esterases are widely used in food processing industry, but there is little information concerning enzymes involved in decompositions of esters contributing to pollution of environment. Vinyl acetate (an ester of vinyl alcohol and acetic acid) is a representative of volatile organic compounds (VOCs) in decomposition, of which hydrolyses and oxidoreductases are mainly involved. Their activities under periodically changing conditions of environment are essential for the removal of dangerous VOCs. Esterase and alcohol/aldehyde dehydrogenase activities were determined in crude cell extract from Pseudomonas fluorescens PMC 2123 after vinyl acetate induction. All examined enzymes exhibit their highest activity at 30-35 °C and pH 7.0-7.5. Esterase preferably hydrolyzed ester bonds with short fatty chains without plain differences for C2 or C4. Comparison of Km values for alcohol and aldehyde dehydrogenases for acetaldehyde suggested that this metabolite was preferentially oxidized than reduced. Activity of alcohol dehydrogenase reducing acetaldehyde to ethanol suggested that one mechanism of defense against the elevated concentration of toxic acetaldehyde could be its temporary reduction to ethanol. Esterase activity was inhibited by phenylmethanesulfonyl fluoride, while β-mercaptoethanol, dithiothreitol, and ethylenediaminetetraacetic acid had no inhibitor effect. From among metal ions, only Mg(2+) and Fe(2+) stimulated the cleavage of ester bond.
酯酶在食品加工业中被广泛使用，但关于参与酯分解导致环境污染的酶的信息却很少。醋酸乙烯酯（乙烯醇和乙酸的酯）是挥发性有机化合物（VOCs）分解中的典型代表，其分解主要涉及水解和氧化还原酶。它们在环境条件周期性变化下的活性对于去除危险的挥发性有机化合物至关重要。在醋酸乙烯酯诱导后，测定了荧光假单胞菌PMC 2123粗细胞提取物中的酯酶和醇/醛脱氢酶活性。所有检测的酶在30-35°C和pH 7.0-7.5时表现出最高活性。酯酶优先水解具有短脂肪链的酯键，对C2或C4没有明显差异。乙醛的醇脱氢酶和醛脱氢酶的Km值比较表明，这种代谢物被优先氧化而非还原。将乙醛还原为乙醇的醇脱氢酶活性表明，抵御有毒乙醛浓度升高的一种机制可能是将其暂时还原为乙醇。苯甲基磺酰氟抑制酯酶活性，而β-巯基乙醇、二硫苏糖醇和乙二胺四乙酸没有抑制作用。在金属离子中，只有Mg(2+)和Fe(2+)刺激酯键的裂解。
