CYCLIC ALPHA-1,4-GLUCAN FORMATION BY BACTERIAL ALPHA-AMYLASES

Cyclic alpha-1,4-glucan formation from synthetic amylose by hydroquino ne glucosylating enzyme (HGE), which is a saccharifying alpha-amylase, was investigated. Upon analysis of reaction products from synthetic a mylose, glucans which were not hydrolyzed by glucoamylase were detecte d with HPAEC in reaction mixtures. The glucans were hydrolyzed by HGE to maltooligosaccharides and hydrolyzed to glucose by the combination of HGE and glucoamylase. From these results, these glucans might be co nsidered to be cyclic alpha-1,4-glucans. In order to demonstrate that these glucans were cyclic alpha-1,4-glucans, phenol-sulfate test, Somo gyi-Nelson test, and tritium labeling test of reducing ends were condu cted. From results of these tests, it was confirmed that these compoun ds were saccharides and did not have reducing ends. Furthermore, the m olecular weight of each glucan was determined using TOF-MS spectrometr y. Each molecular weight agreed with that of cyclic glucans theoretica lly calculated. One of these glucans was purified and was identified t o be gamma-cyclodextrin. These results demonstrate that HGE formed cyc lic alpha-1,4-glucans. Cyclic alpha-1,4-glucans were also detected in the reaction mixtures of bacterial saccharifying alpha-amylase and bac terial liquefying alpha-amylase.