Cyclodextrin Glucanotransferase from Bacillus circulans DF 9R: structure-function relationship

COSTA, HERNÁN; FERRAROTTI, SUSANA; BISCOGLIO DE JIMÉNEZ BONINO, MIRTHA

Mar del Plata, Buenos Aires, Argentina

Congreso; SAIB 2007; 2007

SAIB

Cyclodextrin glucanotransferase (CGTase; EC 2.4.1.19) is a member of the a-amylase family and catalyses the conversion of starch and related glucans alpha (1¨4) into cyclodextrins (CD) through intramolecular transglycosylation as well as transglycosylation intermolecular reactions and a week starch hydrolysis. Three Histidine residues (H140, H233 and H327) are conserved in most a-amylases and other related enzymes and in all known CGTases and are located in conserved regions. Enzyme treatment with 14C ethoxyformyc anhydride, tryptic digestion, mass spectrometry and amino acid sequence analysis  allowed us to show that H233 is the most reactive His residue and play an important role in hydrolytic and alpha-, beta-CD formation activity. Moreover, we found that this enzyme is the only member of a 38 CGTase group having Glutamine instead of Glycine in the -6 subsite, a very conserved region involved in the substrate binding cleft. This finding supports the fact that the enzyme produces an a-CD/ƒÀ-CD ratio higher than those from other Bacillus circulans strains which is important for industrial applications.