Generality
Threonine (T or THR) is an amino acid, or one of the monomers that make up proteins; it is also a quaternary compound, as structured by four elements: carbon, hydrogen, oxygen and nitrogen. Its brute formula is C 4 H 9 NO 3 and has a molecular weight of 119.12u (or Dalton).
That of threonine is called a polar molecule; this means that in the side chain it contains charged groups at physiological pH, therefore they contribute to the so-called hydrogen bonds; the same side chain (equipped with a hydroxyl OH) can be the object of glycation, or has the ability to bind to a glucose molecule. This characteristic is also shared by serine (another essential amino acid) and in the next paragraph we will understand why.
Furthermore, it is said that the structure of threonine (L-) is chiral, that is to say that it is not superimposable (in the 3 dimensions); its enantiomeric (and therefore specular) form is D-threonine.
Functions
From the metabolic point of view, besides constituting a plastic molecule of protein polymers (destined to the constitution of tissues, certain hormones, neurotransmitters, cellular channels, immunoglobulins etc.), threonine acts as a carrier (transporter) for groups phosphate (PO43-) of phosphoproteins (eg, milk caseins), thanks to their ability to receive them at the side chain. This process allows the chemical-physical characteristics of the polymer in question to be transformed and takes place by means of an enzyme catalyst protein kinase. Certainly, the most well-known phosphorylation is that of the transfer of the phosphate group from ATP (Adenosin Tri Phosphate) or from GTP (Guanosin Tri Phosphate) to threonine or serine or tyrosine.
Nevertheless, threonine participates in many synthesis or metabolizing reactions; for example, it is involved in the metabolism of creatine, other amino acids, cobalamin (vit. B12), neurotransmitters (adrenaline and choline) etc.
Not to mention, then, its interaction with selenium, an antioxidant mineral, or the fundamental role in the hepatic metabolic processes of waste molecules.
WARNING! Based on a study by Young et al. (1989; Young & Pellet, 1990; Zello et al., 1995), such as leucine, valine and lysine, also threonine is more subject to energy oxidation than other amino acids, which is why it is logical to think that it may require a superior income in the sportsman .
Food Sources and Deficiency
The dietary sources of threonine are mainly: the egg, dairy products, meat and fish.
The daily requirement of threonine is about 0.95g / day (8-20mg / kg in the adult) and it is one of the amino acids that are most easily lacking in the vegan diet, that is the one totally devoid of ingredients of animal origin; it is, for example, the limiting amino acid of rice and, after lysine, is also scarce in other widely consumed cereals.
The mild deficiency of threonine can cause strong psychological irritability and personality disorders; the severe one is difficult to define but certainly very serious. The excess of threonine, on the other hand, is related to a surge in azotemia, with relative impairment of the organs responsible for metabolism and the elimination of excess in the long term.
Threonine supplements are marketed mainly for its potential ability to promote digestive functions, mental health and the synthesis of collagen and elastin.
