So transketilase is the enzyme that catalyze the transfer of the two carbon component from one sugar molecule onto another sugar molecule. The question is, how does that reaction actually take place? Well, that reaction occurs as a result of the presence of an important Cofactor molecule, a prosthetic group known as Thiamine Pyrophosphate or TPP. And what Thiamine Pyrophosphate actually does is it helps carry out this particular reaction. It acts as a nucleophile, as we'll see in just a moment. So let's begin with this diagram here.