An investigation on acarbose inhibition and the number of active sites in an amylopullulanase (L14-APU) from an Iranian Bacillus sp.

An amylopullulanase (L-14-APU) from an Iranian thermophilic bacterium was purified and the effect of acarbose, as a general inhibitor of alpha-amylases, on pullulan and starch hydrolysis catalyzed by L-14-APU was investigated. The inhibition is a competitive type whereas inhibition constants for pullulan and starch are 99 mu M and 72 mu M, respectively. Investigation of the reaction rate in a system contains competitive substrates and the inhibition type of acarbose in presence of different substrates suggests that L-14-APU possesses only one active site for two activities. The analysis of metal ions and other reagents effects has shown that Ca2+, Mg2+, Mn2+ and Co2+ enhanced both activities of the enzyme while N-bromosuccinimide treatment leads to the complete inactivation of the enzyme. The enzyme activity increased in the presence of low concentration of SDS as a surfactant.