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Diacylglycerol acyltransferase 1 is activated by phosphatidate and inhibited by SnRK1‐catalyzed phosphorylation
Author(s) -
Caldo Kristian Mark P.,
Shen Wei,
Xu Yang,
HanleyBowdoin Linda,
Chen Guanqun,
Weselake Randall J.,
Lemieux M. Joanne
Publication year - 2018
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.14029
Subject(s) - diacylglycerol kinase , biochemistry , phosphatidate , acyltransferase , chemistry , phosphorylation , enzyme , microbiology and biotechnology , biology , protein kinase c
Summary Diacylglycerol acyltransferase 1 (DGAT1) catalyzes the final and committed step in the Kennedy pathway for triacylglycerol ( TAG ) biosynthesis and, as such, elucidating its mode of regulation is critical to understand the fundamental aspects of carbon metabolism in oleaginous crops. In this study, purified Brassica napus diacylglycerol acyltransferase 1 (Bna DGAT 1) in n‐dodecyl‐β‐ d ‐maltopyranoside micelles was lipidated to form mixed micelles and subjected to detailed biochemical analysis. The degree of mixed micelle fluidity appeared to influence acyltransferase activity. Bna DGAT 1 exhibited a sigmoidal response and eventual substrate inhibition with respect to increasing concentrations of oleoyl‐CoA. Phosphatidate ( PA ) was identified as a feed‐forward activator of Bna DGAT 1, enabling the final enzyme in the Kennedy pathway to adjust to the incoming flow of carbon leading to TAG . In the presence of PA , the oleoyl‐CoA saturation plot became more hyperbolic and desensitized to substrate inhibition indicating that PA facilitates the transition of the enzyme into the more active state. PA may also relieve possible autoinhibition of Bna DGAT 1 brought about by the N‐terminal regulatory domain, which was shown to interact with PA . Indeed, PA is a key effector modulating lipid homeostasis, in addition to its well recognized role in lipid signaling. Bna DGAT 1 was also shown to be a substrate of the sucrose non‐fermenting‐1‐related kinase 1 (Sn RK 1), which catalyzed phosphorylation of the enzyme and converted it to a less active form. Thus, this known regulator of carbon metabolism directly influences TAG biosynthesis.