Tayyaba Huma, Ghulam Mustafa, Ayesha sethi, Arooma Maryam, Muhammad Ali
Alpha amylase has a wide range of applications in starch processing, textile industry and its role as a detergent is also well defined. In this study rational approach of protein engineering to analyse the nature of the active site of thermostable alpha amylases via in silico computational tools was excercised. Sequential and structural analysis of alpha amylases from Pyrococcus furiosus (100ºC-105ºC), Bacillus licheniformis (90-95ºC) and Bacillus amyloliquefaciens (72ºC) was carried out. Sequential analysis of hyperthermophilic and thermophilic alpha amylases of studied organisms revealed high AT content in nucleotide sequences. Ratio of charged residues such as Asp, Glu, Arg, His and Lys were found higher as compared to neutral amino residues i.e. Asn, Ser and Thr in hyperthermostable Pyrococcus furiosus and Bacillus licheniformis alpha amylases which stay active at optimum temperature of >90ºC. Role of Asp, Glu, Asp, and Tyr was also observed in activity of alpha amylases, retrieved from different organisms. Tyrosine residue was found as a conserved residue in the active sites of alpha amylases especially of Bacillus alpha amylases. Phenylalanine at position 109 and isoleucine at position 428 were observed only in hyperthermostable Pyrococcus furiosus alpha amylase. While all others were found to have Tyr and Val at position 109 and 428, respectively which could be a reason behind the thermostability of Pyrococcus furiosus alpha amylase. In addition substantial amount of aromatic residues were observed in the active site of hyperthermophilic Pyrococcus furiosus alpha amylase. A large number of aromatic residues in the active sites of these alpha amylases and their interactions are expected to be involved in the overall stability of the enzymes.
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