Diglyceride acyltransferase

Diglyceride acyltransferase (or O-acyltransferase), DGAT, catalyzes the formation of triglycerides from diacylglycerol and Acyl-CoA. The reaction catalyzed by DGAT is considered the terminal and only committed step in triglyceride synthesis and to be essential for the formation of adipose tissue.^[1] The protein is homologous to other membrane-bound O-acyltransferases.

Isoforms

There are two isozymes of DGAT encoded by the genes DGAT1^[2] and DGAT2.^[3] Although both isozymes catalyze similar reactions, they have no sequence homology to each other.

Knockout studies

Mice with genetic disruption of the dgat1 or dgat2 genes have been made by the Farese laboratory at UCSF. Surprisingly, DGAT1^−/− mice^[4] are healthy and fertile and have no changes in triglyceride levels. These mice are also lean and resistant to diet-induced obesity, consequently generating interest in DGAT1 inhibitors for the treatment of obesity. In contrast, DGAT2^−/− mice^[5] have reduced triglyceride levels but are lipopenic, suffer from skin barrier abnormalities (including the inability to retain moisture), and die shortly after birth.

Therapeutic application

DGAT-1 inhibitors have potential for the treatment of obesity^[6]^[7] and a number of DGAT-1 inhibitors are in clinical trials for this indication.^[8]

References

↑ Cases S, Smith SJ, Zheng YW, Myers HM, Lear SR, Sande E, Novak S, Collins C, Welch CB, Lusis AJ, Erickson SK, Farese RV (October 1998). "Identification of a gene encoding an acyl CoA:diacylglycerol acyltransferase, a key enzyme in triacylglycerol synthesis". Proceedings of the National Academy of Sciences of the United States of America. 95 (22): 13018–23. doi:10.1073/pnas.95.22.13018. PMC 23692. PMID 9789033.
↑ Oelkers P, Behari A, Cromley D, Billheimer JT, Sturley SL (October 1998). "Characterization of two human genes encoding acyl coenzyme A:cholesterol acyltransferase-related enzymes". The Journal of Biological Chemistry. 273 (41): 26765–71. doi:10.1074/jbc.273.41.26765. PMID 9756920.
↑ Cases S, Stone SJ, Zhou P, Yen E, Tow B, Lardizabal KD, Voelker T, Farese RV (October 2001). "Cloning of DGAT2, a second mammalian diacylglycerol acyltransferase, and related family members". The Journal of Biological Chemistry. 276 (42): 38870–6. doi:10.1074/jbc.M106219200. PMID 11481335.
↑ Smith SJ, Cases S, Jensen DR, Chen HC, Sande E, Tow B, Sanan DA, Raber J, Eckel RH, Farese RV (May 2000). "Obesity resistance and multiple mechanisms of triglyceride synthesis in mice lacking Dgat". Nature Genetics. 25 (1): 87–90. doi:10.1038/75651. PMID 10802663.
↑ Stone SJ, Myers HM, Watkins SM, Brown BE, Feingold KR, Elias PM, Farese RV (March 2004). "Lipopenia and skin barrier abnormalities in DGAT2-deficient mice". The Journal of Biological Chemistry. 279 (12): 11767–76. doi:10.1074/jbc.M311000200. PMID 14668353.
↑ Chen HC, Farese RV (March 2005). "Inhibition of triglyceride synthesis as a treatment strategy for obesity: lessons from DGAT1-deficient mice". Arteriosclerosis, Thrombosis, and Vascular Biology. 25 (3): 482–6. doi:10.1161/01.ATV.0000151874.81059.ad. PMID 15569818.
↑ Cheng D, Iqbal J, Devenny J, Chu CH, Chen L, Dong J, Seethala R, Keim WJ, Azzara AV, Lawrence RM, Pelleymounter MA, Hussain MM (October 2008). "Acylation of acylglycerols by acyl coenzyme A:diacylglycerol acyltransferase 1 (DGAT1). Functional importance of DGAT1 in the intestinal fat absorption". The Journal of Biological Chemistry. 283 (44): 29802–11. doi:10.1074/jbc.M800494200. PMC 2662058. PMID 18768481.
↑ "Pfizer, Bristol finalize deal on metabolic drugs". Reuters. 2007-08-27. Retrieved 2007-08-27.

Transferases: acyltransferases (EC 2.3)

2.3.1: other than amino-acyl groups	acetyltransferases: Acetyl-Coenzyme A acetyltransferase N-Acetylglutamate synthase Choline acetyltransferase Dihydrolipoyl transacetylase Acetyl-CoA C-acyltransferase Beta-galactoside transacetylase Chloramphenicol acetyltransferase N-acetyltransferase Serotonin N-acetyl transferase HGSNAT ARD1A Histone acetyltransferase P300/CBP NAT2 palmitoyltransferases: Carnitine O-palmitoyltransferase CPT1 CPT2 Serine C-palmitoyltransferase SPTLC1 SPTLC2 other: Acyltransferase like 2 Aminolevulinic acid synthase Beta-ketoacyl-ACP synthase Glyceronephosphate O-acyltransferase Lecithin—cholesterol acyltransferase Glycerol-3-phosphate O-acyltransferase 1-acylglycerol-3-phosphate O-acyltransferase 2-acylglycerol-3-phosphate O-acyltransferase ABHD5

2.3.2: Aminoacyltransferases	Gamma-glutamyl transpeptidase Peptidyl transferase Transglutaminase Tissue transglutaminase Keratinocyte transglutaminase Factor XIII

2.3.3: converted into alkyl on transfer	Citrate synthase ATP citrate lyase HMG-CoA synthase Malate synthase

Enzymes

Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Catalytically perfect enzyme Coenzyme Cofactor Enzyme catalysis Enzyme kinetics Lineweaver–Burk plot Michaelis–Menten kinetics

Regulation	Allosteric regulation Cooperativity Enzyme inhibitor

Classification	EC number Enzyme superfamily Enzyme family List of enzymes

Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list)

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