Structure basis of a mutant α-CGTase tyrosine167histidine from Bacillus sp. 602-1 with enhanced α-CD productions

The crystal structure of Y167H mutant α-CGTase was determined at 2.1Å. The overall structure was like that of the Y195I mutant α-CGTase, with minor difference in flexible domains and the shift of one Ca2+. The H167 in Y167H mutant α-CGTase moved slightly to surface of the enzyme. In the static models of enzyme-sugar complex, the side chain of H167 is above 5Å far from the sugar chain instead of 3Å of the Y167 in the Y195I mutant. H167 could bind the sugar chain at initial stage better due to its charges and location. This work helps explain the mechanism of the enhanced production of α-CD by Y167H mutant α-CGTase.