CRYSTALLOGRAPHIC ANALYSES OF THE FLEXIBILITY OF THE P-O-C ESTER LINK IN PHOSPHOENOLPYRUVATES. Thomas P. O'Connor, Jr.^1,2, Robert H. Blessing¹, ¹Hauptman-Woodward Medical Research Institute, 73 High Street, Buffalo, New York 14203-1196 USA, ²Graduate Studies Program in Natural Sciences, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York 14263 USA

Analyses of soft modes of internal torsional vibrations about the P-O and O-C bonds and P-O-C valence angle bending vibrations in phosphoenolpyruvate species in crystals will be described. A database of room-temperature anisotropic mean-square atomic displacement parameters for 19 crystallographic occurrences of H₃Pep, H₂Pep-, HPep²-, and Pep^3- phosphoenolpyruvate species has been analyzed to complement a recent analysis of the corresponding valence and conformational geometries [M. Souhassou, P. M. Schaber, and R. H. Blessing (1996), Acta Cryst., Part B, submitted].

Pep^3- = (O^-)₂P(O)-O-C(CH₂)-CO₂^-

Phosphoenolpyruvates are of interest because, among the various species involved in the ATP cycle of bioenergetics, phosphoenolpyruvate has the highest free energy of hydrolysis or phosphate group transfer potential. We are grateful to several colleagues for indispensable help with this work: Prof. Tadeusz Lis and his co-workers at the University of Wroclaw determined or refined most of the phosphoenolpyruvate crystal structures that formed the basis of our studies, and they kindly provided parameter files in machine-readable form. Prof. Kenneth Trueblood of UCLA provided his THMA14 program. Prof. Bryan Craven of the University of Pittsburgh provided his and Dr. Xiao-Min He's EKRT program, and Professor Hans-Beat Buergi and Dr. Juerg Hauser of the University of Bern provided their PEANUT program. We also acknowledge with gratitude research support from NIH Grant No. PO1 GM46733.