Mutations in the Substrate-Binding Pocket of DiacylGlycerol Acyltransferase Alter the Fatty Acid Composition of Triacylglycerides in Yeast

Triacylglycerols (TAGs) are the main components of food oils and fats. The fatty acid composition of TAGs varies for different oils and fats. Specific enzymes sequentially add three fatty acids to the glycerol backbone of TAGs. Diacylglycerol acyltransferase or DGAT adds the third and ultimate fatty acid to the glycerol backbone at the sn-3 position. In this study, we characterized the substrate-binding pocket of enzyme DGAT1 from Arabidopsis thaliana through heterologous expression in the DGAT mutant of Saccharomyces cerevisiae. We performed site saturation mutagenesis on 10 amino acid residues in the catalytic site and examined their effects on the fatty acid profile of yeast cells. Our results indicate that mutations F373G, T240I, M289F, and V248I impact the yeast TAG profile either in terms of the total saturation level or the carbon chain length of the fatty acids, suggesting that they change the DGAT's substrate preference. This offers insights into crucial amino acid residues in the DGAT binding pocket which can be engineered for fine tuning the lipid profile. In summary, we have harnessed the power of enzyme engineering to modify the fatty acyl makeup of triglycerides and created a sustainable platform for the production of customized alternative lipids.