Inhibition of Escherichia coli cytidine deaminase by a phosphapyrimidine nucleoside.

摘要: Abstract The nature of the interaction between Escherichia coli cytidine deaminase and phosphapyrimidine nucleoside 1 has been studied kinetically spectrophotometrically. Compound was designed as a transition-state analog, is potent, slow-binding inhibitor (Ashley, G. W., Bartlett, P. A. (1982) Biochem. Biophys. Res. Commun. 108, 1467-1474). We present evidence that binding reversible, with no covalent linkage enzyme 1. At pH 6, rate recovery activity from dissociation E X I complex strongly dependent on concentration I, indicating dissociates reversibly. UV difference spectroscopy reveals chromophore unaltered to enzyme, thus eliminating possibility modification enzyme. For active beta-anomers deaminase, following kinetic parameters were determined at 6: kon = 8300 M-1 S-1, koff 7.8 10(-6) Ki 0.9 nM. also able observe characterize time-dependent inhibition E. by tetrahydrouridine, 3. This involves initial formation loose (KD 1.2 microM), followed isomerization in slow step give more tightly bound (Ki 0.24 microM) forward reverse constants kf 3.81 min-1 kr 0.95 min-1, respectively.