Plant TAG also can serve as a feedstock for petrochemical alternatives such as biolubricants, biopolymers, and biodiesel ( Metzger and Bornscheuer, 2006). Not only does TAG serve as an energy reserve to fuel germination and early seedling growth, but this highly reduced form of carbon is a nutritional source of dietary oil for humans and animals. Triacylglycerol ( TAG) is the predominant component of the seed oil of oleaginous plants. Based on these results, a model is proposed illustrating the role of the N-terminal domain of BnaDGAT1 as a positive and negative modulator of TAG biosynthesis. The conserved amino acid residues in the loop interacting with CoA were identified, revealing details of this important regulatory element for allosteric regulation. The three-dimensional NMR solution structure of the allosteric site revealed an α-helix with a loop connecting a coil fragment. Enzyme activation, on the other hand, is prevented under limiting acyl-CoA conditions (low acyl-CoA-to-CoA ratio), whereby CoA acts as a noncompetitive feedback inhibitor through interaction with the same folded segment. Under increasing acyl-CoA levels, the binding of acyl-CoA with this noncatalytic site facilitates homotropic allosteric activation. We show that the disordered region has an autoinhibitory function and a dimerization interface, which appears to mediate positive cooperativity, whereas the folded segment of the cytosolic region was found to have an allosteric site for acyl-CoA/CoA. The N-terminal domain is not necessary for acyltransferase activity and is composed of an intrinsically disordered region and a folded segment. Here, we report that the hydrophilic N-terminal domain of Brassica napus DGAT1 (BnaDGAT1 1-113) regulates activity based on acyl-CoA/CoA levels. The biochemical regulation of TAG assembly remains one of the least understood areas of primary metabolism to date.
Diacylglycerol acyltransferase 1 (DGAT1) is an integral membrane enzyme catalyzing the final and committed step in the acyl-coenzyme A (CoA)-dependent biosynthesis of triacylglycerol ( TAG).
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