Figure 1.

Cytosolic glucose enters glycolysis and pentose phosphate pathways. Pyruvate enters mitochondria where it is converted into acetyl-CoA then used in TCA cycle. Excess citrate is transported from the mitochondria into cytosol. ATP citrate lyase (ACL) converts the cytosolic citrate into acetyl-CoA that is converted into malonyl-CoA by acetyl-CoA carboxylase (ACC), the first committing step of fatty acid (FA) synthesis. After FA synthesis, triacylglycerol (TAG) is synthesized in the endoplasmic reticulum (ER) via Kennedy pathway and then accumulated in lipid bodies (LB). Acyl-CoA is used for acylation of glycerol-3- phosphate to form lysophosphatidic acid (LPA) that is further acylated to form phosphatidicacid (PA). PA is dephosphorylated to form diacylglycerol (DAG), which is then acylated to produce TAG catalyzed by DAG acyltransferase (DGAT). TAG can also be synthesized by phospholipid (PL):DAG acyltransferase (PDAT) using PL and DAG as substrates. Ex novo FA accumulation also uses Kennedy pathway. FA is metabolized by β- oxidation pathway in peroxisome. Abbreviations: 6PGL, 6-Phosphogluconolactonase; 6PDG, 6-Phosphogluconate dehydrogenase; α-KG, alpha-ketoglutarate; DHAP, dihydroxyacetone phosphate; FAT1, FAT Atypical Cadherin 1; G3P, glyceraldehyde3-phosphate; G6PD, glucose-6-phosphate dehydrogenase; GPD1, glycerol-3-phosphate dehydrogenase; GUT2, glycerol-kinase; Mfe1, multifunctional enzyme 1; ME, malic enzyme; OAA, oxaloacetate; PEP, phosphoenolpyruvate; Pex3 and Pex10, peroxisome biogenesis factor 3 and 10, respectively; Pox1 to Pox6, acyl-CoA oxidases 1–6, respectively; TGL3 and TGL4, TAG lipase 3 and 4, respectively; PYC, pyruvatecarboxylase; TCA, tricarboxylic acid cycle. Yellow box: schematic diagram of aerobic pathways for ω-3 and ω-6 FA biosynthesis. Abbreviations: C16E, EL1, C20E and D9E are C16/C18, C18, C20/C22, Δ-9 elongases, respectively. D4D, D5D, D6D, D8D, D9D, D12D, D15D and D17D are Δ-4, Δ-5, Δ-6, Δ-8, Δ-9, Δ-12, Δ-15, and Δ-17 desaturases, respectively.