Structure Thymidine phosphorylase

arg-171, ser-186, , lys-190 interactions thymine in ligand site of thymidine phosphorylase

thymidine phosphorylase protein dimer identical subunits – reported molecular weight of 90,000 daltons in escherichia coli. has s-shape length of 110 Å , width of 60 Å. each monomer composed of 440 amino acids , composed of small α-helical domain , large α/β domain. surface of enzyme smooth except 10 Å deep , 8 Å wide cavity between 2 domains contains thymine, thymidine, , phosphate binding sites. detailed analysis of binding sites shows arg-171, ser-186, , lys-190 important residues in binding pyrimidine base. residues arg-171 , lys-190 close o4 , o2 of thymine ring, respectively, , can stabilize intermediate state.

the terminal amino group of lys-190, forms hydrogen bond 3′-hydroxyl of thymidine ribose moiety in place donate proton thymine n1 during intermediate state. of late 2007, 6 structures have been solved class of enzymes, pdb accession codes 1azy, 1otp, 1tpt, 1uou, 2j0f, , 2tpt.