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Mechanistic evidence for a front-side, SNi-type reaction in a retaining glycosyltransferase

Mechanistic evidence for a front-side, SNi-type reaction in a retaining glycosyltransferase
Mechanistic evidence for a front-side, SNi-type reaction in a retaining glycosyltransferase
A previously determined crystal structure of the ternary complex of trehalose-6-phosphate synthase identified a putative transition state–like arrangement based on validoxylamine A 6?-O-phosphate and uridine diphosphate in the active site. Here linear free energy relationships confirm that these inhibitors are synergistic transition state mimics, supporting front-face nucleophilic attack involving hydrogen bonding between leaving group and nucleophile. Kinetic isotope effects indicate a highly dissociative oxocarbenium ion–like transition state. Leaving group 18O effects identified isotopically sensitive bond cleavages and support the existence of a hydrogen bond between the nucleophile and departing group. Brønsted analysis of nucleophiles and Taft analysis highlight participation of the nucleophile in the transition state, also consistent with a front-face mechanism. Together, these comprehensive, quantitative data substantiate this unusual enzymatic reaction mechanism. Its discovery should prompt useful reassessment of many biocatalysts and their substrates and inhibitors
1552-4450
631-638
Lee, Seung Seo
ee34fa26-5fb6-48c8-80c2-1f13ec4ccceb
Hong, Sung You
6b5558cb-eab9-4b5b-a8dc-ea37301f0480
Errey, James C.
9bcf401d-303c-489e-834b-35710e6837c9
Izumi, Atsushi
24be8e15-6a87-45d6-89b5-33a33fe20254
Davies, Gideon J.
61049906-cf8c-4c45-afb6-edbea5efd8f1
Davis, Benjamin G.
2a8a594f-5d71-455a-bd99-d1366c1028cc
Lee, Seung Seo
ee34fa26-5fb6-48c8-80c2-1f13ec4ccceb
Hong, Sung You
6b5558cb-eab9-4b5b-a8dc-ea37301f0480
Errey, James C.
9bcf401d-303c-489e-834b-35710e6837c9
Izumi, Atsushi
24be8e15-6a87-45d6-89b5-33a33fe20254
Davies, Gideon J.
61049906-cf8c-4c45-afb6-edbea5efd8f1
Davis, Benjamin G.
2a8a594f-5d71-455a-bd99-d1366c1028cc

Lee, Seung Seo, Hong, Sung You, Errey, James C., Izumi, Atsushi, Davies, Gideon J. and Davis, Benjamin G. (2011) Mechanistic evidence for a front-side, SNi-type reaction in a retaining glycosyltransferase. Nature Chemical Biology, 7 (9), 631-638. (doi:10.1038/NCHEMBIO.628).

Record type: Article

Abstract

A previously determined crystal structure of the ternary complex of trehalose-6-phosphate synthase identified a putative transition state–like arrangement based on validoxylamine A 6?-O-phosphate and uridine diphosphate in the active site. Here linear free energy relationships confirm that these inhibitors are synergistic transition state mimics, supporting front-face nucleophilic attack involving hydrogen bonding between leaving group and nucleophile. Kinetic isotope effects indicate a highly dissociative oxocarbenium ion–like transition state. Leaving group 18O effects identified isotopically sensitive bond cleavages and support the existence of a hydrogen bond between the nucleophile and departing group. Brønsted analysis of nucleophiles and Taft analysis highlight participation of the nucleophile in the transition state, also consistent with a front-face mechanism. Together, these comprehensive, quantitative data substantiate this unusual enzymatic reaction mechanism. Its discovery should prompt useful reassessment of many biocatalysts and their substrates and inhibitors

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Published date: August 2011
Organisations: Chemistry

Identifiers

Local EPrints ID: 340227
URI: http://eprints.soton.ac.uk/id/eprint/340227
ISSN: 1552-4450
PURE UUID: de6d98e7-b930-4895-9e40-815bc964597e
ORCID for Seung Seo Lee: ORCID iD orcid.org/0000-0002-8598-3303

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Date deposited: 21 Sep 2012 12:30
Last modified: 17 Dec 2019 01:37

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