title: Biochemical characterization of human acyl coenzyme A: 2-monoacylglycerol acyltransferase-3 (MGAT3).
abstract: MGAT3 catalyzes the synthesis of 1,2-diacylglycerol from 2-monoacylglycerol in an acyl CoA-dependent reaction. Although initially identified as an MGAT enzyme, MGAT3 is more closely related to DGAT2 than to MGAT1 and MGAT2. Furthermore, MGAT3 possesses both DGAT and MGAT activities, in vitro. MGAT3 is almost exclusively expressed in the small intestine in humans, suggesting that it has a role in dietary fat absorption. Although identified many years ago, little information is available regarding the contribution of MGAT3 to triacylglycerol biosynthesis.
  
  
  
  This study confirmed the initial observations that MGAT3 possessed both MGAT and DGAT activities. When expressed in cells in culture, MGAT3 stimulated lipid droplet growth, but unlike DGAT2, does not become concentrated around the lipid droplet surface. We also characterized the MGAT activity of an MGAT3 mutant in which a conserved cysteine was changed to a tyrosine residue. Lastly, although they share significant sequence identity, MGAT3 is a much more stable protein than DGAT2, yet they are both polyubiquitinated and degraded through ER-associated degradation by the proteasome.
  
  
  
  Our findings provide additional evidence that MGAT3 likely functions as a TG synthase in cells.
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Curtis
authors.initials: C
authors.lastname: Brandt
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: McFie
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada. Electronic address: scot.stone@usask.ca.
authors.forename: Scot J
authors.initials: SJ
authors.lastname: Stone
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism*; D000217:Acyltransferases / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D051048:Diacylglycerol O-Acyltransferase / Q000032:analysis / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D066292:Lipid Droplets / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D000214:Acyl Coenzyme A; D014280:Triglycerides; D000217:Acyltransferases; C494881:DGAT1 protein, human; C494885:DGAT2 protein, human; D051048:Diacylglycerol O-Acyltransferase; C021802:2-acylglycerol O-acyltransferase
keywords: Diacylglycerol; Diacylglycerol acyltransferase; Lipid droplet; Monoacylglycerol acyltransferase; Triacylglycerol