Abstract: The present invention relates to a method of identifying, screening or selecting a compound which binds to the transglycosylation site of a recombinant glycosyl transferase, comprising the steps consisting in: a) bringing said compound into contact with said recombinant protein before, after or at the same time as said recombinant protein is brought into contact with a transglycosylation activity inhibitor, said inhibitor being labeled with a label that generates a direct or indirect signal, b) studying said signal linked to said recombinant protein, the binding of said compound to the transglycosylation site being deduced from the difference between the signal obtained in step b) and the signal obtained in the absence of said compound.