   1.14.19.58 | L460F/P461E/P462T |
site-directed, structure-guided mutagenesis, the mutant exhibit similar activity to the wild-type SttH, with tryptophan as a substrate, but shows a complete switch in regioselectivity compared to the wild-type enzyme without impacting on catalytic efficiency: 75% 5-chlorination is observed for the substrate 3-indolepropionate with the mutant in comparison to 90% 6-chlorination of 3-indolepropionate for the wild-type SttH. SttH is more like PyrH than PrnA, with insertions present in PyrH and SttH between residues SttH 155 and 167 and a deletion between SttH 457 and 464 compared with PrnA, the mutation, the only differences evident in the active-site region between the structures of PyrH and SttH are those of PyrH residues F451, E452 and T453 and SttH L460, P461 and P462. These residues are of particular interest because they are in close proximity to the active site in PyrH and SttH, and are positioned directly above the alpha-amino acid moiety of the substrate, tryptophan. Moreover, there isa loop insertion in PrnA in this region that is suggested to contribute to its regioselectivity. Each of these residues is mutated in SttH to the corresponding residue in PyrH, that is, L460F, P461E and P462T. Individually, each mutation reduces the relative activity of the enzyme with tryptophan, but does not have a significant effect on the observed regioselectivity, with 6-chlorotryptophan remaining the major product |
744705 |
