Intracellular rebinding of transition-state analogues provides extended in vivo inhibition lifetimes on human purine nucleoside phosphorylase.

ABSTRACT: Purine nucleoside phosphorylase (PNP) is part of the human purine salvage pathway. Its deficiency triggers apoptosis of activated T-cells, making it a target for T-cell proliferative disorders. Transition-state analogues of PNP bind with picomolar (pm) dissociation constants. Tight-binding PNP inhibitors show exceptionally long lifetimes on the target enzyme. We solve the mechanism of the target residence time by comparing functional off-rates in vitro and in vivo We report in vitro PNP-inhibitor dissociation rates (t_½) from 3 to 31 min for seven Immucillins with dissociation constants of 115 to 6 pm Treatment of human erythrocytes with DADMe-Immucillin-H (DADMe-ImmH, 22 pm) causes complete inhibition of PNP. Loss of [¹⁴C]DADMe-ImmH from er

SUBMITTER: Gebre ST 

PROVIDER: S-EPMC5612120 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature