20 amino acids levy

2003/08/08 Kortabitarte Egiguren, Irati - Elhuyar Zientzia

• Biokimika

This deviation of polarized light to the right or to the left is related to the chirality, according to which the molecules are dextrogiras or levogiras respectively. But, what is that least known chemical property in molecules? In summary, the quirality is related to the spatial conformation of the components of the molecule. In fact, if a levogira molecule is placed in front of a mirror, we will see the dextrospin molecule, that is, the image of the unsurpassed mirror. It is what happens with the hands of human beings, who can never overlap. And according to this quirality, the chemical properties of the molecule change.

The same thing does not occur in amino acids. Although polarized light can be directed to the right or to the left, its chemical properties will not vary depending on it. However, in nature it has been detected that the 20 amino acids are levógiros and an explanation has been found.

Serine, one of the 20 amino acids, is very demanding in terms of quirality. Most amino acids are able to form weak linkages with other amino acids without taking into account their quirality. Serine, on the other hand, is quite peculiar in this aspect, since it forms more solid cluster structures of binding of eight molecules. These clusters, known as oktameros, will be formed by dextrógiras or levógiras molecules, but never by a mixture between them. Curiously, once formed the octamero, this one is able to establish solid relations with the amino acids of the same quirality and sugars of the counterwatch. Therefore, they believe that serine plays a role similar to the doorman of a discotheque, that is, if the amino acid is levógiro forward and, if not, encourages them to change the quirality. In fact, in nature there is the serine levógira, so that all the amino acids become levóginos.

However, if, despite being molecules with different types of volutes, the chemical properties do not change, why does the domain of serine levógira versus serine dextrógira? This will be the next challenge of experts. The theory of serine tells us about the importance of quirality in the origin of life.