To adequately understand the biochemical properties of lipase from Aspergillus flavus, the knowledge of (i) the molecular structure and (ii) the interaction between amino acid sequence, structure and function are required to pave the way for the improvement of their catalytic efficiency and industrial applicability which can be achieved through protein engineering (Bassegoda et al., 2012 Mala & Takeuchi, 2008). However, there is limited information available on the molecular and structural characteristics of Aspergillus flavus lipases. Numerous reports described the production and biochemical characterisation of lipases from the filamentous fungi Aspergillus flavus (Colla et al., 2015 Kareem et al., 2017 Toscano et al., 2013). Fungi are widely recognized as reliable sources of lipases and in particular, filamentous fungi are the preferred choice (Joshi & Kuila, 2018 Kumar, 2015) largely due to the high catalytic activity and ease of extraction from fermentation broth (Mehta et al., 2017). In the last decades, lipases of microbial origin have attracted much attention within the fast-growing enzyme technology in comparison to plant and animal lipases due to their varied catalytic activities, high stability, ease of genetic manipulation, regular supply due to absence of seasonal fluctuation and the rapid growth of microbes (Singh et al., 2016). Their catalytic versatility is a driver for the increased demand for lipases in chemical, detergent, pharmaceutical, food and oil industries (Elemuo et al., 2019 Jaiswal et al., 2017). In addition to hydrolysis, lipases catalyse other reactions which includes esterification, transesterification, and interesterification under reduced water environments (Geoffry & Achur, 2018 Sharma et al., 2016). Lipases catalyse the hydrolysis of long-chain triacylglycerols to generate fatty acids and glycerol (Schmid, 1998). On the other hand, lipases are useful in multiple industrial processes, such as biodiesel production, in the textile industry for improving absorbency during dying, in the leather industry for dehairing and degreasing in leather making, and in the food production such as baking and in food flavouring (Mehta et al., 2017 Raveendran et al., 2018). This family of enzymes have also been used as markers for the diagnosis of diseases such as cystic fibrosis and atherosclerosis (Etschmaier et al., 2011 Loli et al., 2015) thus underpinning their relevance in the biomedical industry. Lipases (triacylglycerol acyl hydrolases EC 3.1.1.3) are enzymes produced by a variety of living organisms, ranging from plants to animals, and micro-organism and are widely used as biocatalysts capable of contributing towards improving the underexploited fat and oil biotechnology industry (Sharma & Kanwar, 2014). The findings on the structural and molecular properties of Aspergillus flavus lipase in this work will be crucial in future studies aiming at engineering the enzyme for biotechnology applications. This is a short peptide sequence that marks a protein for transport across the cell membrane and indicates that AFL is an extracellular lipase. A signal sequence of 37 amino acids was revealed at the N-terminal of the polypeptide. O-glycosylation sites were predicted at residues 355, 358, 360 and 366. N-glycosylation sites were predicted at residues 164, 236 and 333, with potentials of 0.7250, 0.7037 and 0.7048, respectively. A search of the lipase engineering database using AFL sequence revealed that it belongs to the class GX-lipase, superfamily abH23 and homologous family abH23.02, molecular weight and isoelectric point values of 46.95 KDa and 5.7, respectively. The 3-Dimensional structural model shared 34.08% sequence identity with a lipase from Yarrowia lipolytica covering 272 amino acid residues of the template model. This lid protects the active site, control the catalytic activity and substrate selectivity in lipases. A catalytic active site lid domain composed of TYITDTIIDLS amino acids sequence was also revealed. Alignment of the amino acid sequence with other lipases revealed the presence GHSLG sequence which is the lipase consensus sequence Gly-X1-Ser-X2-Gly indicating that it a classical lipase. ![]() An open reading frame of 420 amino acid sequence was obtained and designated as Aspergillus flavus lipase (AFL) sequence. The gene coding for extracellular triacylglycerol lipase was isolated from Aspergillus flavus species, sequenced, and characterised using bioinformatics tools. A lipolytic fungus was isolated and subsequently identified based on the ITS sequence analysis as putative Aspergillus flavus with accession number LC424503. Lipases are enzymes of industrial importance responsible for the hydrolysis of ester bonds of triglycerides.
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