Premium
Catalytic activities of intracellular dimeric neopullulanase on cyclodextrin, acarbose and maltose
Author(s) -
Cheong KyungA,
Kim TaeJip,
Yoon JongWon,
Park CheonSeok,
Lee TaeSoo,
Kim YoungBae,
Park KwanHwa,
Kim JungWan
Publication year - 2002
Publication title -
biotechnology and applied biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.468
H-Index - 70
eISSN - 1470-8744
pISSN - 0885-4513
DOI - 10.1042/ba20010052
Subject(s) - maltose , chemistry , acarbose , hydrolysis , dimer , cyclodextrin , monomer , amylase , starch , substrate (aquarium) , biochemistry , chromatography , enzyme , organic chemistry , biology , ecology , polymer
Multi‐substrate specificity of neopullulanase towards cyclodextrin, acarbose and maltose was investigated using a clone originating from Bacillus stearothermophilus IMA6503. The enzyme purified from Escherichia coli harbouring the corresponding nplA gene hydrolysed β ‐cyclodextrin ( β ‐CD) to maltose and glucose. It exhibited substrate preference for β ‐CD, starch and pullulan in the proportions of 10.4:1.2:1. The enzyme not only hydrolysed acarbose, an α ‐amylase inhibitor, to a pseudotrisaccharide (PTS) and glucose, but also transferred PTS to glucose, forming isoacarbose. Moreover, it hydrolysed maltose to glucose and transferred the glucose to another maltose molecule to form panose when maltose was present at a low concentration (0.5%) in the reaction solution. The enzyme catalysed condensation between two maltose molecules and subsequent hydrolysis of the resulting 6 2 ‐ O ‐ α ‐maltosyl‐maltose to glucose and panose, when maltose concentration was increased to 20%. Neopullulanase was likely to be present in monomer–dimer equilibrium with a molar ratio of 1:9 in 50 mM sodium acetate buffer (pH 6.0). The association–dissociation equilibrium of neopullulanase was shifted to monomerization by KCl. When the content of monomer increased in the reaction mixture, the specific activity towards soluble starch increased to 150%, while that towards β ‐CD decreased to 80%. Therefore, multi‐substrate specificity of neopullulanase was likely to be modulated by the shift of monomer–dimer association equilibrium.