text: Methylthioadenosine nucleosidase are enzymes that catalyse the hydrolytic deadenylation reaction of 5'-methylthioadenosine and S-adenosylhomocysteine. It is also regarded as an important target for antibacterial drug discovery because it is important in the metabolic system of bacteria and only produced by bacteria.  Given the different distance between nitrogen atom of adenine and the ribose anomeric carbon (see in the diagram in this section), the transition state structure can be defined by early or late dissociation stage. Based on the finding of different transition state structures, Schramm and coworkers designed two transition state analogues mimicking the early and late dissociative transition state. The early and late transition state analogue shown binding affinity (Kd) of 360 and 140 pM, respectively.