Enzymological Characterization of Atm, the First Laccase from Agrobacterium sp. S5-1, with the Ability to Enhance In Vitro digestibility of Maize Straw

Laccase is an enzyme that catalyzes oxidation of phenolic compounds, diamines and aromatic amines. In this study, a novel laccase-like gene (atm) in a ligninolyitic isolate Agrobacterium sp. S5-1 from soil humus was identified and heterologously expressed in Escherichia coli. Atm exhibited its maximal activity at pH 4.5 and at 50°C. This enzyme was tolerant to high temperature, a broad range of pH, heavy metal ions (Co3+, Mn2+, Cu2+ and Ni2+, 20 mM) and all tested organic solvents. Furthermore, Atm significantly (ppin vitro digestibility of maize straw, thus suggesting that Atm has an application potential for bioconversion of lignin rich agricultural byproducts into animal feed and cellulosic ethanol.漆酶（Laccase）是一类能够催化酚类化合物、二胺及芳香胺发生氧化反应的酶。本研究从土壤腐殖质中分离得到一株木质素分解农杆菌（Agrobacterium）属菌株S5-1，从中鉴定出一种新型类漆酶基因atm，并将该基因在大肠杆菌（Escherichia coli）中进行异源表达。Atm的最适反应pH为4.5，最适反应温度为50℃。该酶具有良好的高温耐受性、宽泛的pH适应范围，对20 mM的Co³+、Mn²+、Cu²+及Ni²+等重金属离子以及所有受试有机溶剂均具备耐受性。此外，Atm可显著提升玉米秸秆的体外消化率，这表明Atm在将富含木质素的农业副产物生物转化为动物饲料及纤维素乙醇方面具有应用潜力。