Abstract
A novel esterase gene, e69, was cloned from Erythrobacter seohaensis SW-135, which was isolated from a tidal flat sediment of the Yellow Sea in Korea. This gene is 825 bp in length and codes for a 29.54 kDa protein containing 274 amino acids. Phylogenetic analysis showed that E69 is a new member of the bacterial lipolytic enzyme family IV. This enzyme exhibited the highest level of activity toward p-nitrophenyl (NP) butyrate but little or no activity toward the other p-NP esters tested. The optimum temperature and pH of the catalytic activity of E69 were 60°C and pH 10.5, respectively. The enzyme exhibited stable activity over a wide range of alkaline pH values (7.5–9.5). In addition, E69 was found to be a halotolerant esterase as it exhibited the highest hydrolytic activity in the presence of 0.5 M NaCl and was still active in the presence of 3 M NaCl. Moreover, it possessed some degree of tolerance to Triton X-100 and several organic solvents. Through homology modeling and comparison with other esterases, it was suggested that the absence of the cap domain and its narrow substrate-binding pocket might be responsible for its narrow substrate specificity. Sequence and structural analysis results suggested that its high ratio of negatively to positively charged residues, large hydrophobic surface area, and negative electrostatic potential on the surface may be responsible for its alkaline adaptation. The results of this study provide insight into marine alkaliphilic esterases, and the unique properties of E69 make it a promising candidate as a biocatalyst for industrial applications.
Highlights
Esterases (EC 3.1.1.1) are lipolytic enzymes that catalyze the cleavage of ester bonds of short-chain fatty esters in aqueous media and the reverse reaction in organic solvents and are widely expressed in various organisms, including bacteria, fungi, vertebrates, and invertebrates (Arpigny and Jaeger, 1999; Fuciños et al, 2012; Lópezlópez et al, 2014)
The deduced amino acid sequence of the putative esterase gene was compared with known esterase amino acid sequences available from the GenBank nr database and the Protein Data Bank (PDB) database, which revealed relatively low identities with known esterases
The phylogenetic tree constructed with 17 bacterial lipolytic enzyme families showed that E69 belongs to family IV (Figure 1)
Summary
Esterases (EC 3.1.1.1) are lipolytic enzymes that catalyze the cleavage of ester bonds of short-chain fatty esters in aqueous media and the reverse reaction in organic solvents and are widely expressed in various organisms, including bacteria, fungi, vertebrates, and invertebrates (Arpigny and Jaeger, 1999; Fuciños et al, 2012; Lópezlópez et al, 2014). Esterases have diverse industrial applications because of their broad substrate specificity, stereoselectivity, no requirements for cofactors, and high stability in organic solvents (Bornscheuer, 2002; Sayali and Surekha, 2013). They have wide applications as biocatalysis in food, detergent, textile, paper, pharmaceutical and agrochemical. Since high salt concentration tends to reduce the water activity like organic solvents, esterases from marine microorganisms have potentials in industrial biocatalytic processes in the presence of organic solvents, high salinity, and low water activity environments, such as stereospecific reaction, esterification, transesterification, and polymerization reaction (Fuciños et al, 2012). An increasing number of esterases with habitat-specific characteristics have been identified from marine environments or marine microorganisms, including esterases that are thermostable (Li et al, 2015; Huang et al, 2016), coldactive (Fu et al, 2011; Jiang et al, 2012b; De Santi et al, 2014; Tchigvintsev et al, 2015), alkaliphilic (Park et al, 2007; De Santi et al, 2014), halotolerant (Jiang et al, 2012a; Fang et al, 2014; De Santi et al, 2016a; Zhang et al, 2017), or tolerant to solvents (Zhang et al, 2014; Guo et al, 2016)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
