Figure 4.
(A) The sequences illustrated are those of the phylogenetic group E of Arabidopsis glycosyltransferases (Li et al, 2001). Regioselective glycosylation of esculetin falls into two distinct subsets in Group E, with the exception of UGTs 72B1 and 72B3, which suggests that a switching event in regioselectivity has occurred during evolution (Lim et al, 2003a). Sequences not analysed are labelled in black. (B) UGTs 74F1 and 74F2 are 82% identical at the amino-acid sequence level, but display different regioselectivity towards salicylic acid. (C) UrdGT1b and UrdGT1c are Streptomyces fradiae glycosyltransferases involved in the biosynthesis of the antibiotic urdamycin. Gene shuffling using the DNA sequences encoding these two glycosyltransferases enabled the generation of an engineered protein (cyan) with a catalytic activity different from the parental enzymes (Hoffmeister et al, 2002).