Desaturase

A Desaturase is an enzyme which removes two hydrogen atoms from an organic compound, creating a carbon/carbon double bond. Desaturases are classified as
* delta - indicating that the double bond is created at a fixed position from the carboxyl group of a fatty acid (for example, Δ⁹desaturase creates a double bond at the 9th position from the carboxyl end).
* omega (e.g. ω³desaturase) - indicating the double bond is created at a specific position from the methyl end of the fatty acid.

In the biosynthesis of essential fatty acids, an elongase alternates with different desaturases (for example, Δ⁶desaturase) repeatedly inserting an ethyl group, then forming a double bond.

Role in human metabolism

Three desaturases occur in humans: Δ⁹desaturase, Δ⁶desaturase and Δ⁵ desaturase.

Δ⁹desaturase, also known as Stearoyl-CoA desaturase-1, is used to synthesize oleic acid, a monounsaturated, ubiquitous component of all cells in the human body. Δ⁹desaturase produces oleic acid by desaturating stearic acid, a saturated fatty acid either synthesized in the body from palmitic acid, or ingested directly.

Δ⁶ and Δ⁵ desaturases are required for the synthesis of highly unsaturated fatty acids such as eicosopentaenoic and docosahexaenoic acids (synthesized from linolenic acid), and arachidonic acid (synthesized from linoleic acid). This is a multi-stage process requiring successive actions by elongase and desaturase enzymes. The genes coding for Δ⁶ and Δ⁵ desaturase production have been located on human chromosome 11.

References

cite journal
author=Nakamura MT, Nara TY
title=Structure, function and dietary regulation of Δ6, Δ5 and Δ9 desaturases
journal=Annual Review of Nutrition
issue=24
pages=345–76
year=2004
doi=10.1146/annurev.nutr.24.121803.063211