Eukaryotic lipid-biosynthetic enzymes: the same but not the same

The discovery that different eukaryotic enzymes catalyse the same lipid-biosynthetic reaction has paralleled the recognition that segregated pools of lipids have unique biological functions. This review considers enzymes involved in the synthesis of diverse classes of lipids--glycerolipid precursors, phospholipids, sterols and eicosanoids--and summarizes recent data that show that these duplicate enzymes are frequently encoded by different genes and have unique subcellular locations. Does this duality merely represent redundancy or do the different isoforms provide pools of lipids for specific biological purposes?