2ZM9 image
Entry Detail
PDB ID:
2ZM9
Keywords:
Title:
Structure of 6-Aminohexanoate-dimer Hydrolase, A61V/S112A/A124V/R187S/F264C/G291R/G338A/D370Y mutant (Hyb-S4M94) with Substrate
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2008-04-14
Release Date:
2009-04-14
Method Details:
Experimental Method:
Resolution:
1.50 Å
R-Value Free:
0.19
R-Value Work:
0.17
R-Value Observed:
0.17
Space Group:
P 32 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:6-aminohexanoate-dimer hydrolase
Mutations:A61V, S112A, A124V, R187S, F264C, G291R, G338A, D370Y
Chain IDs:A
Chain Length:392
Number of Molecules:1
Biological Source:Flavobacterium sp.
Primary Citation
Two alternative modes for optimizing nylon-6 byproduct hydrolytic activity from a carboxylesterase with a beta-lactamase fold: X-ray crystallographic analysis of directly evolved 6-aminohexanoate-dimer hydrolase.
Protein Sci. 18 1662 1673 (2009)
PMID: 19521995 DOI: 10.1002/pro.185

Abstact

Promiscuous 6-aminohexanoate-linear dimer (Ald)-hydrolytic activity originally obtained in a carboxylesterase with a beta-lactamase fold was enhanced about 80-fold by directed evolution using error-prone PCR and DNA shuffling. Kinetic studies of the mutant enzyme (Hyb-S4M94) demonstrated that the enzyme had acquired an increased affinity (K(m) = 15 mM) and turnover (k(cat) = 3.1 s(-1)) for Ald, and that a catalytic center suitable for nylon-6 byproduct hydrolysis had been generated. Construction of various mutant enzymes revealed that the enhanced activity in the newly evolved enzyme is due to the substitutions R187S/F264C/D370Y. Crystal structures of Hyb-S4M94 with bound substrate suggested that catalytic function for Ald was improved by hydrogen-bonding/hydrophobic interactions between the Ald--COOH and Tyr370, a hydrogen-bonding network from Ser187 to Ald--NH(3) (+), and interaction between Ald--NH(3) (+) and Gln27-O(epsilon) derived from another subunit in the homo-dimeric structure. In wild-type Ald-hydrolase (NylB), Ald-hydrolytic activity is thought to be optimized by the substitutions G181D/H266N, which improve an electrostatic interaction with Ald--NH(3) (+) (Kawashima et al., FEBS J 2009; 276:2547-2556). We propose here that there exist at least two alternative modes for optimizing the Ald-hydrolytic activity of a carboxylesterase with a beta-lactamase fold.

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