Determinants for Substrate Specificity of Protein Phosphatase 2A

Protein phosphatase 2A- (PP2A-) catalyzed dephosphorylation of target substrate proteins is widespread and critical for cellular function. PP2A is predominantly found as a heterotrimeric complex of a catalytic subunit (C), a scaffolding subunit (A), and one member of 4 families of regulatory subunits (B). Substrate specificity of the holoenzyme complex is determined by the subcellular locale the complex is confined to, selective incorporation of the B subunit, interactions with endogenous inhibitory proteins, and specific intermolecular interactions between PP2A and target substrates. Here, we discuss recent studies that have advanced our understanding of the molecular determinants for PP2A substrate specificity

Synthesis of 3-[(\u3cem\u3eN\u3c/em\u3e-Carboalkoxy)ethylamino]-Indazole-Dione Derivatives and Their Biological Activities on Human Liver Carbonyl Reductase

A series of indazole-dione derivatives were synthesized by the 1,3-dipolar cycloaddition reaction of appropriate substituted benzoquinones or naphthoquinones and N-carboalkoxyamino diazopropane derivatives. These compounds were evaluated for their effects on human carbonyl reductase. Several of the analogs were found to serve as substrates for carbonyl reductase with a wide range of catalytic efficiencies, while four analogs display inhibitory activities with IC50 values ranging from 3–5 μM. Two of the inhibitors were studied in greater detail and were found to be noncompetitive inhibitors against both NADPH and menadione with KI values ranging between 2 and 11 μM. Computational studies suggest that conformation of the compounds may determine whether the indazole-diones bind productively to yield product or nonproductively to inhibit the enzyme