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Publication Abstract from PubMed

GtfC-type 4,6-alpha-glucanotransferase (alpha-GT) enzymes from Glycoside Hydrolase Family 70 (GH70) are of interest for the modification of starch into low-glycemic index food ingredients. Compared to the related GH70 GtfB-type alpha-GTs, found exclusively in lactic acid bacteria (LAB), GtfCs occur in non-LAB, share low sequence identity, lack circular permutation of the catalytic domain, and feature a single-segment auxiliary domain IV and auxiliary C-terminal domains. Despite these differences, the first crystal structure of a GtfC, GbGtfC-DeltaC from Geobacillus 12AMOR1, and the first one representing a non-permuted GH70 enzyme, reveals high structural similarity in the core domains with most GtfBs, featuring a similar tunneled active site. We propose that GtfC (and related GtfD) enzymes evolved from starch-degrading alpha-amylases from GH13 by acquiring alpha-1,6 transglycosylation capabilities, before the events that resulted in circular permutation of the catalytic domain observed in other GH70 enzymes (glucansucrases, GtfB-type alpha-GTs). AlphaFold modeling and sequence alignments suggest that the GbGtfC structure represents the GtfC subfamily, although it has a so far unique alternating alpha-1,4/alpha-1,6 product specificity, likely determined by residues near acceptor binding subsites +1/+2.

Crystal Structure of 4,6-alpha-Glucanotransferase GtfC-DeltaC from Thermophilic Geobacillus 12AMOR1: Starch Transglycosylation in Non-Permuted GH70 Enzymes.,Pijning T, Te Poele EM, de Leeuw TC, Guskov A, Dijkhuizen L J Agric Food Chem. 2022 Nov 28. doi: 10.1021/acs.jafc.2c06394. PMID:36442227^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.