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Title: Mechanism-based post-translational modification and inactivation in terpene synthases

Terpenes are ubiquitous natural chemicals with diverse biological functions spanning all three domains of life. In specialized metabolism, the active sites of terpene synthases (TPSs) evolve in shape and reactivity to direct the biosynthesis of a myriad of chemotypes for organismal fitness. As most terpene biosynthesis mechanistically involves highly reactive carbocationic intermediates, the protein surfaces catalyzing these cascade reactions possess reactive regions possibly prone to premature carbocation capture and potentially enzyme inactivation. Here, we show using proteomic and X-ray crystallographic analyses that cationic intermediates undergo capture by conserved active site residues leading to inhibitory self-alkylation. Furthermore, the level of cation-mediated inactivation increases with mutation of the active site, upon changes in the size and structure of isoprenoid diphosphate substrates, and alongside increases in reaction temperatures. TPSs that individually synthesize multiple products are less prone to self-alkylation then TPSs possessing relatively high product specificity. In total, the results presented suggest that mechanism-based alkylation represents an overlooked mechanistic pressure during the evolution of cation-derived terpene biosynthesis.
Authors:
 [1] ;  [2] ;  [2] ;  [1]
  1. The Salk Inst. for Biological Studies, La Jolla, CA (United States)
  2. The Scripps Research Inst., La Jolla, CA (United States); The Salk Inst. for Biological Studies, La Jolla, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231; AC02-693-05CH11231
Type:
Published Article
Journal Name:
ACS Chemical Biology
Additional Journal Information:
Journal Volume: 10; Journal Issue: 11; Journal ID: ISSN 1554-8929
Publisher:
American Chemical Society (ACS)
Research Org:
Salk Inst. for Biological Studies, La Jolla, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES
OSTI Identifier:
1221692
Alternate Identifier(s):
OSTI ID: 1345035