Abstract: Pyrimidine nucleoside phosphorylase(PYNP) catalyzes the reversible phosphorolysis of pyrimidines in the nucleotide synthesis salvage pathway.The enzyme has two structure states: non-active opened structure and active closed structure.During change from non-active opened structure to active closed structure, the protein loop connecting domain α to domain α/β becomes bent remarkablely, which results in two domains closed up, and binding pocket reduce obviously.Setting about from the inactive-open X-ray structure, applying the method of molecular dynamic simulation, putting the ligand in the active-pocket, we carry out a dynamic simulation in the CVFF force-field for the entire system.The structures obstained are more approximately to the active-close X-ray structures, it proves that the rigid movement of the domains is arouse by the inducing effect of the ligand molecules.

Key words: Pyrimidine nucleoside phosphorylase, Dynamic simulation, Induction