Skip to main content
. Author manuscript; available in PMC: 2008 Oct 1.
Published in final edited form as: Curr Opin Chem Biol. 2007 Sep 14;11(5):529–536. doi: 10.1016/j.cbpa.2007.07.013

Figure 8.

Figure 8

Alignment of inosine, phosphate and His257 near the transition state in the catalytic site of human PNP (lower figure). Vibrational modes of the protein are coupled into His 257 and to the phosphate to create periodic compression motions of the three oxygen atoms shown in bold [39,43••]. The effects of these compression modes is to destabilize electrons from the central oxygen, causing them to depart with the leaving group, creating a ribooxacarbenium ion at the transition state. The upper table resolves the relative contributions of BIE and the intrinsic KIE to the experimentally observed V/K KIE.