4PFH: Crystal structure of engineered D-tagatose 3-epimerase PcDTE-IDF8

Citation:
Abstract
Functional promiscuity of enzymes can often be harnessed as the starting point for the directed evolution of novel biocatalysts. Here we describe the divergent morphing of an engineered thermostable variant (Var8) of a promiscuous D-tagatose epimerase (DTE) into two efficient catalysts for the C3 epimerization of D-fructose to D-psicose and of L-sorbose to L-tagatose. Iterative single-site randomization and screening of 48 residues in the first and second shells around the substrate-binding site of Var8 yielded the eight-site mutant IDF8 (ninefold improved kcat for the epimerization of D-fructose) and the six-site mutant ILS6 (14-fold improved epimerization of L-sorbose), compared to Var8. Structure analysis of IDF8 revealed a charged patch at the entrance of its active site; this presumably facilitates entry of the polar substrate. The improvement in catalytic activity of variant ILS6 is thought to relate to subtle changes in the hydration of the bound substrate. The structures can now be used to select additional sites for further directed evolution of the ketohexose epimerase.
PDB ID: 4PFHDownload
MMDB ID: 124057
PDB Deposition Date: 2014/4/29
Updated in MMDB: 2017/12
Experimental Method:
x-ray diffraction
Resolution: 1.9  Å
Source Organism:
Similar Structures:
Biological Unit for 4PFH: dimeric; determined by author and by software (PISA)
Molecular Components in 4PFH
Label Count Molecule
Proteins (2 molecules)
2
D-tagatose 3-epimerase
Molecule annotation
Chemicals (7 molecules)
1
3
2
2
3
2
* Click molecule labels to explore molecular sequence information.

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