|CAO, NANCY - California Institute Of Technology|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 8/1/2013
Publication Date: 12/31/2014
Citation: Cao, H., Cao, N.L. 2015. Sequence analysis of diacylglycerol acyltransferases. In: Rao, A.R., Govil, J.N., editors. Biotechnology, Volume 6, Bioinformatics and Computational Biology. Houston, TX:Studium Press LLC. p. 71-104.
Interpretive Summary: Triacylglycerols (TAGs) are the major molecules of energy storage in eukaryotes. They provide fatty acids for membrane biogenesis and lead to obesity due to excessive accumulation in adipose tissues. Therefore, understanding the mechanism and regulation of TAG biosynthesis in plants and animals will have tremendous potential in creating new oilseed crops with value-added properties and providing information for therapeutic intervention for obesity and related diseases. One key enzyme for TAG biosynthesis is diacylglycerol acyltransferase (DGAT) because it catalyzes the last and rate-limiting step of TAG biosynthesis in eukaryotic organisms. However, it is difficult to study this enzyme because multiple isoforms of DGAT are present in most plants, animals, fungi and human. One way to study this enzyme is to perform multiple sequencing analyses to identify conserved sequence motifs and amino acid residues in diverse organisms since critical amino acid residues of proteins are conserved during the evolution. This chapter updated the sequencing analysis of 164 DGAT sequences from 91 organisms ranging from plants, animals and fungi. We identified conserved sequence motifs and amino acid residues in all DGAT1, DGAT2 and DGAT3 subfamilies and discussed the importance of some conserved residues with site-directed and natural mutants. Our analyses support the concept that the catalytic and regulatory domains of DGATs are located at the C- and N-termini of the enzymes, respectively. Therefore, sequence analysis described in this chapter should facilitate studying the structure-function relationship of DGATs with the ultimate goal of identifying critical amino acid residues. This will guide the construction of superb enzymes for metabolic engineering and rational design of DGAT inhibitors to be used for obesity and related diseases.
Technical Abstract: Diacylglycerol acyltransferases (DGATs) catalyze the final step of triacylglycerol (TAG) biosynthesis in eukaryotes. DGATs esterify sn-1,2-diacylglycerol with a long-chain fatty acyl-CoA. Plants and animals deficient in DGATs accumulate less TAG and over-expression of DGATs increases TAG. DGAT knockout mice are resistant to diet-induced obesity and lack milk secretion. Therefore, understanding the roles of DGATs will help to create transgenic plants with value-added properties and provide information for nutritional and therapeutic intervention for obesity and related diseases. We identified conserved sequence motifs and amino acid residues of 164 DGATs from 91 organisms including 39 plants, 26 animals and 26 fungi. Phylogenetic analysis separates these proteins into 59 DGAT1s from 48 organisms, 74 DGAT2s from 61 organisms and 31 DGAT3s from 23 organisms. Most of the conserved residues and sequence motifs are located at the carboxyl termini of DGATs, suggesting the location of the catalytic domains. Natural and site-directed mutants in DGATs have demonstrated the importance of some conserved residues in TAG biosynthesis. The sequence analysis should facilitate studying the structure-function relationship of DGATs with the ultimate goal to identify critical amino acid residues for metabolic engineering and drug discovery.