Chemist RUDN clarified the principle of action of enzymes that create omega-6 fats

Fatty acids are a long chain of carbon atoms with branches. There is a carboxyl group (COOH) at one end, and a methyl group (CH3) at the other. Some carbon atoms can be connected not by a single bond, but by a double one — such acids are called unsaturated. They are usually called by the position of the double bonds, counting from the methyl or carboxyl end. In the first case, the name is marked with the letter omega, in the second — delta. For example, in vaccenic acid, the only double bond is at the 7 carbon atom from the methyl ring or at the 11 — from the carboxyl ring, so its name means either ω7 or Δ11. It is assumed that the enzymes that add new double bonds to the chain also "count" the desired carbon atom from one or the other end. The chemist RUDN showed for the first time that for some enzymes that produce vital omega-6 fats, this is not the case.

"Enzymes are extremely sensitive to the position and geometric configuration of newly introduced double bonds. How they do their counting is a long-standing question, to which there is no clear answer yet. Although it is assumed that the counting comes from the methyl or carboxyl end, there is no exact understanding of this mechanism yet. We have shown that for at least some enzymes, the counting is not carried out as previously thought,"- Sergey Goryainov, head of the Laboratory of Mass Spectrometry and high-resolution NMR Spectroscopy, RUDN University.

Enzymes that create double bonds in fatty acid chains are called desaturases. Each desaturase is designed to create an acid with a double bond only for a specific carbon atom. For example, omega-6 desaturase creates double bonds only at the sixth carbon atom, counting from the methyl end. Chemists have shown that for fatty acids with multiple double bonds, enzymes "count" the desired atom not from the end of the chain, but from the position of the already existing double bond. This was done using the example of omega-6 desaturases obtained from two types of bacteria - Gloeobacter violaceus and Synechocystis.

Cell cultures of two types of bacteria were grown on a solid nutrient medium, and then moved to a liquid medium, where their DNA was isolated. Chemists also measured the composition of fatty acids in bacteria. To accurately determine the position of the double bond, chemists used mass spectrometry. All these procedures were repeated at least three times. Comparing the presence of genes encoding desaturases and the composition of fatty acids, chemists concluded how desaturases determine the desired carbon atom in the chain. It turned out that these enzymes count three carbon atoms from the double bond towards the methyl end of the chain and create a double bond there.

"Our results show that the bacterial Δ12(ω6) desaturases count from the already existing double bond, and not from the ends. At the same time, the length of the chain does not matter,"- Sergey Goryainov.

The results are published in the journal Biochimie.