Cloning and In Silico Analysis of a High-Temperature Inducible Lipase from Brevibacillus

Abstract

The genus Brevibacillus comprises diverse collection of gram-positive/gram-variable, endospore-forming, rod-shaped, aerobic/facultative anaerobic bacteria inhabitant of varied environmental habitats contributing many industrial enzymes. A thermophilic lipolytic bacterium was previously isolated from a hot spring of Orissa, India, and identified as Brevibacillus sp. AK-P2 via 16S rRNA gene technology. A 750-bp lipase gene from Brevibacillus sp. AK-P2 was isolated and sequenced, which encoded a deduced polypeptide of 250 amino acid residues. The comparative analysis of amino acid composition among thermostable and mesostable homologue of Brevibacillus lipases ascertains the role of neutral, charged, and aromatic amino acid residues in thermostability. Three amino acid residues Ser 94, His 242, and Asp 213 were identified from this putative lipase of Brevibacillus sp. AK-P2 as catalytic triad. The consensus ‘P-loop’ motif (-[AG]-X4-G-K-[ST]-) previously reported for Bacillus thermoalkalophilic lipases is modified to (-[AT]-[GE]-X5-G-[RQ]-[S]-) inBrevibacillus lipases. Multiple sequence alignment (MSA) revealed that there is a methionine residue (M) in the oxyanion hole consensus sequence of thermostable Brevibacillus lipases. The frequency of occurrence of AXXXA motif is more for thermophilic Brevibacillus lipases than their mesophilic counterparts ensures strong van der Waals interaction and stabilization of proteins. Higher percentage of Alanine (A) in thermophilic Brevibacillus lipases attributed toward thermostabilization of lipases. Codon usage analysis revealed that there was intermediate codon usage bias in lipase-coding genes, and the same supports our hypothesis that GC mutation pressure might determine codon usage bias.