The presence of the -OH group allows threonine to be involved in reactions such as phosphorylation. Within proteins, threonine can also bind to carbohydrate molecules, known as glycoprotein.
This is for example the case of mucin, the glycoprotein of mucus, which is rich in threonine. The coating of mucin with carbohydrates prevents it from being broken down.
The mucus then carries out its various functions. It humidifies the inhaled air and warms it up. It also captures different particles (bacteria, viruses, dust) and destroys them thanks to the antibodies, enzymes and proteins it contains.
Mucus is also present in the intestines. It favours the implantation of bifidobacteria ("good bacteria") and contributes to the diversification of the microbiota.