Loading…
Theoretical Studies on the Catalytic Mechanism and Substrate Diversity for Macrocyclization of Pikromycin Thioesterase
Polyketide synthases (PKSs) share a subset of biosynthetic steps in construction of a polyketide, and the offload from the PKS main module of specific product release is most often catalyzed by a thioesterase (TE). In spite of the fact that various PKS systems have been discovered in polyketide bios...
Saved in:
Published in: | ACS catalysis 2018-05, Vol.8 (5), p.4323-4332 |
---|---|
Main Authors: | , , , , , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | Polyketide synthases (PKSs) share a subset of biosynthetic steps in construction of a polyketide, and the offload from the PKS main module of specific product release is most often catalyzed by a thioesterase (TE). In spite of the fact that various PKS systems have been discovered in polyketide biosynthesis, the molecular basis of TE-catalyzed macrocyclization remains challenging. In this study, MD simulations and QM/MM methods were combined to investigate the catalytic mechanism and substrate diversity of pikromycin (PIK) TE with two systems (PIK-TE-1 and PIK-TE-2), where substrates 1 and 2 correspond to TE-catalyzed precursors of 10-deoxymethynolide and narbonolide, respectively. The results showed that, in comparison with PIK-TE-2, system PIK-TE-1 exhibited a greater tendency to form a stable prereaction state, which is critical to macrocyclization. In addition, the structural characteristics of prereaction states were uncovered through analyses of hydrogen-bonding and hydrophobic interactions, which were found to play a key role in substrate recognition and product release. Furthermore, potential energy surfaces were calculated to study the molecular mechanism of macrocyclization, including the formation of tetrahedral intermediates from re- and si-face nucleophilic attacks and the release of products. The energy barrier of macrocyclization from re-face attack was calculated to be 16.3 kcal/mol in PIK-TE-1, 3.6 kcal/mol lower than that from si-face attack and 4.1 kcal/mol lower than that from re-face attack in PIK-TE-2. These results are in agreement with experimental observations that the yield of 10-deoxymethynolide is superior to that of narbonolide in PIK TE catalyzed macrocyclization. Our findings elucidate the catalytic mechanism of PIK TE and provide a better understanding of type I PKS TEs in protein engineering. |
---|---|
ISSN: | 2155-5435 2155-5435 |
DOI: | 10.1021/acscatal.8b01156 |