FAD2

FAD2 refers to a family of enzymes known as delta-12 fatty acid desaturases, typically described in plants and some microbes as the enzymes that convert oleic acid (18:1) into linoleic acid (18:2) by introducing a second double bond in the fatty acyl chain. In most contexts, FAD2 functions as part of the endoplasmic reticulum membrane system, where it participates in the biosynthesis of polyunsaturated fatty acids that make up seed and leaf lipids.

Structurally, FAD2 enzymes are membrane-bound proteins characterized by conserved histidine-rich motifs essential for catalytic activity. They require an electron transfer system, usually involving cytochrome b5 and associated reductases, to provide the reducing equivalents needed for desaturation. Some FAD2 proteins contain an integral or associated cytochrome b5 domain, while others rely on separate b5 partners in the cell.

Function and distribution vary by organism but are most intensively studied in plants. In seeds, FAD2 activity directly shapes oil composition by increasing levels of polyunsaturated fatty acids, influencing fluidity and nutritional properties of the oil. Leaves and developing fruits also express FAD2, contributing to membrane lipid remodeling in response to developmental cues and environmental conditions. Although FAD2 is best known for converting oleic to linoleic acid, related omega-6 desaturases operate in different cellular compartments or lineages, including FAD3 and chloroplast-associated desaturases in other species.

Regulation occurs at transcriptional and post-translational levels, with expression often responsive to temperature, light, and hormonal signals. Biotechnological applications focus on manipulating FAD2 to alter seed oil composition, such as increasing oleic acid content for healthier edible oils. Techniques include breeding and gene editing to downregulate or modify FAD2 activity in crops.