Characterization of a recombinant maltogenic amylase from deep sea thermophilic Bacillus sp. WPD616

A maltogenic amylase-producing thermophilic strain WPD616, assigned to Bacillus sp. WPD616 based on 16S rRNA sequence, was isolated from a deep-sea hydrothermal field in west Pacific. Subsequently, a maltogenic amylase gene encoding 588 amino acids from this isolate was cloned and expressed in Escherichia coli as a fusion protein with glutathione S-transferase (GST). The results showed that the recombinant maltogenic amylase had an activity optimum at 50 °C and pH at 6.0. It was active up to 70 °C at pH 6.0 and stable at pHs ranging from 6.0 to 8.0. The recombinant enzyme was active when Chaps, DTT and Tween 20 (0.1% or 1%) were used. However, it can be partially inhibited by 1 mM of EDTA, PMSF or SDS, as well as 0.1% of Triton X-100 or 2-ME, and completely inhibited by 10 mM of PMSF and SDS (10 mM). Its catalytic function was stable in the presence of Li+ and K+ (1 mM or 10 mM), but its activity decreased when Ba2+, Ca2+, Mg2+, Mn2+ (1 mM or 10 mM) and Fe2+ (1 mM) were used. In the presence of Zn2+, Cu2, Fe3+ (1 mM and 10 mM) and Fe2+ (10 mM), no activity was detected.