Investigations of anion binding sites in transition state analogue complexes of creatine kinase by infrared spectroscopy.

Abstract

A specific class of anions inhibit creatine kinase by stabilizing the dead-end complex, enzyme- divalent cat- ion*ADP*creatine (Watts, D. C. (1973) The Enzymes 8, 383-455). The inhibitory action o? the anions is attrib- uted to the ability of the anions to mimic the equatorial PO3 plane formed by the migrating phosphoryl group in the transition state of the reaction. Infrared spec- troscopy has been used to investigate the mode of binding of the inhibitory anions, thiocyanate, azide, and nitrate to the dead-end complex of creatine kinase. The infrared absorptions for these anions undergo characteristic changes in frequency or in multiplicity when the anions are liganded to various divalent cat- ions, and infrared spectra for the enzymic complexes with the anions provide a means for recognizing anion- metal ion coordination at the active site of creatine kinase. Infrared spectra for the complexes of the anions with enzyme