Molecular Cloning and Characterization of an α-Amylase from Pichia burtonii 15-1

Abstract

An α-amylase secreted by Pichia burtonii 15-1 isolated from a traditional starter murcha of Nepal, named Pichia burtonii α-amylase (PBA), was studied. The gene was cloned and its nucleotide sequence was determined. PBA was deduced to consist of 494 amino acid residues. It shared certain degrees of amino acid sequence identity with other homologous proteins: 60% with Schwanniomyces occidentalis α-amylase, 58% with Saccharomycopsis sp. α-amylase, and 47% with Taka-amylase A from Aspergillus oryzae. A three-dimensional structural model of PBA generated using the known three-dimensional structure of Taka-amylase A as a template suggested high structural similarity between them. Kinetic analysis revealed that the K_m values of PBA were lower than those of Taka-amylase A for the oligosaccharides. Although the k_cat values of PBA were lower than those of Taka-amylase A for the oligosaccharide substrates, the k_cat⁄K_m values of PBA were higher.