So where does that hydroxy methyl group come from? Well, from a molecule known as phyton methylene THF, where THF stands for tetrahydropholate. So we have glycine in the presence of water and in the presence of this molecule. Phy ten methylene tetrahydrophoblate basically undergoes a reaction that is catalyzed by serine hydroxy methyl transferase. And so what this enzyme does is it ultimately transfers this group here, shown in blue, as well as uses the water molecule to actually attach that hydroxide group onto glycine. So ultimately, we attach a hydroxy methyl group onto the glycine to form our serene.