Title: Defining the extreme substrate specificity of Euonymus alatus diacylglycerol acetyltransferase, an unusual membrane-bound O-acyltransferase

Abstract

Euonymus alatus diacylglycerol acetyltransferase (EaDAcT) synthesizes the unusually structured 3-acetyl-1,2-diacylglycerols (acetyl-TAG) found in the seeds of a few plant species. A member of the membrane-bound O-acyltransferase (MBOAT) family, EaDAcT transfers the acetyl group from acetyl-CoA to sn-1,2-diacylglycerol (DAG) to produce acetyl-TAG. In vitro assays demonstrated that the enzyme is also able to utilize butyryl-CoA and hexanoyl-CoA as acyl donors, though with much less efficiency compared with acetyl-CoA. Acyl-CoAs longer than eight carbons were not used by EaDAcT. This extreme substrate specificity of EaDAcT distinguishes it from all other MBOATs which typically catalyze the transfer of much longer acyl groups. In vitro selectivity experiments revealed that EaDAcT preferentially acetylated DAG molecules containing more double bonds over those with less. However, the enzyme was also able to acetylate saturated DAG containing medium chain fatty acids, albeit with less efficiency. Interestingly, EaDAcT could only acetylate the free hydroxyl group of sn-1,2-DAG but not the available hydroxyl groups in sn-1,3-DAG or in monoacylglycerols (MAG). Consistent with its similarity to the jojoba wax synthase, EaDAcT could acetylate fatty alcohols in vitro to produce alkyl acetates. Likewise, when coexpressed in yeast with a fatty acyl-CoA reductase capable of producing fatty alcohols, EaDAcT synthesized alkyl acetates althoughmore » the efficiency of production was low. As a result, this improved understanding of EaDAcT specificity confirms that the enzyme preferentially utilizes acetyl-CoA to acetylate sn-1,2-DAGs and will be helpful in engineering the production of acetyl-TAG with improved functionality in transgenic plants.« less

Authors:

Bansal, Sunil ^[1]; Durrett, Timothy P. ^[1]

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+ Show Author Affiliations

1. Kansas State Univ., Manhattan, KS (United States)

Publication Date:

Tue Nov 08 00:00:00 EST 2016

Research Org.:

Colorado State Univ., Fort Collins, CO (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1360143

Grant/Contract Number:  

SC0012459

Resource Type:

Accepted Manuscript

Journal Name:

Bioscience Reports

Additional Journal Information:

Journal Volume: 36; Journal Issue: 6; Journal ID: ISSN 0144-8463

Publisher:

Portland Press - Biochemical Society

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; 60 APPLIED LIFE SCIENCES; acetyltransferase; MBOAT; triacylglycerols; acetyl‐TAGs; substrate specificity