Purification and characterization of a thermostable cyclodextrin glycosyltransferase from Thermoanaerobacter sp. P4

Abstract

Cyclodextrin glycosyltransferase (CGTase, EC 2.4.1.19) from a thermophilic anaerobic bacterium, Thermoanaerobacter sp. P4, was purified by ammonium sulfate precipitation followed by α-cyclodextrin epoxy activated-sepharose 6B column chromatography. Enzyme was purified 141 fold and had the specific activity of 143.8 U/mg proteins. Purification yields after ammonium sulfate precipitation and affinity chromatography were 25.8 and 17.8%, respectively. SDS-PAGE analysis showed that enzyme was purified successfully and had a single band. Molecular weight of the enzyme was determined as 68.7 kDa. The enzyme had optimum cyclization activity at 80 to 90°C and hydrolyzing activity at 90°C and maintained 87 and 95% of these activities at 95°C, respectively. Optimal pH was found as 7.0. It retained full activity at 80°C for 4 h. Enzyme was strongly inhibited by HgSO₄ and AgNO₃. Addition of 1 mM CaCl₂ increased the enzymatic activity up to 7%. This novel enzyme could be a good candidate for industrial applications according to its characteristic found in the current study.

Key words: Cyclodextrin glycosyltransferase, cyclodextrin production, Thermoanaerobacter sp. P4, thermophilic, enzyme purification, enzyme characterization.