Fred Winer - p-(Bromoacetamido)phenyl uridyl pyrophosphate:  an active-site-directed irreversible inhibitor for uridine diphosphate galactose 4-epimerase

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          p-(Bromoacetamido)phenyl uridyl           pyrophosphate:  an active-site-directed irreversible           inhibitor for uridine diphosphate galactose           4-epimerase       
          By Wong, Yun-Hua Huang; Winer, Fredric B.; Frey, Perry A.           From Biochemistry (1979), 18(24), 5332-6. Language:           English        


  The synthesis of p-(bromoacetamido)phenyl uridyl pyrophosphate   (I) is described.  This compd. was an active-site-directed   irreversible inhibitor of Escherichia coli UDP-galactose   4-epimerase.  The inactivation followed pseudo-first-order   kinetics at pH 8.5 in nonnucleophilic buffers, and a satn. effect   was seen in the pseudo-first-order rate const. as the concn. of I   was increased.  The half-satn.  parameter for I in the   inactivation was 0.21 mM, which compared  favorably with the   inhibition const. of 0.3 mM for I acting as a  competitive   reversible inhibitor of the enzyme.  The inactivation   rate  was slow, with a min. half-time of 12 h at pH 8.5 and   27°.  Both  specific and nonspecific alkylation by I   occurred but the nonspecific  alkylation was faster than the   inactivation and the rate of inactivation  correlated well   with the rate of covalent incorporation of 1 mol. of    [14C]-I at the active site.

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