Esterolytic Peptide Dendrimers with a Hydrophobic Core and Catalytic Residues at the Surface

Abstract

Abstract(3S)‐4‐(9‐Fluorenylmethoxycarbonylamino)‐3‐methyl(allyloxycarbonyl)aminoethyloxyacetic acid (1) was prepared from (R)‐3‐aminopropane‐1,2‐diol and used as branching unit for the synthesis of second generation peptide dendrimers with six individually addressable variable amino acid positions. Three pairs of diastereomeric dendrimers were prepared bearing a common hydrophobic core and permutations of the catalytic triad amino acids aspartate, histidine and serine at the surface. Dendrimers with two surface histidine residues catalyzed the hydrolysis of fluorogenic 8‐acyloxypyrene‐1,3,6‐trisulfonates in aqueous buffer pH 6.0 with rate enhancement kcat/kuncat in the 103 range and Michaelis‐Menten constants KM in the 10−4 M range. Substrate recognition involves electrostatic interactions, as shown by competitive inhibition of catalysis observed with pyrene‐1,3,6,8‐tetrasulfonate. The 4‐fold to 7‐fold lowering in KM between the butyryl and nonanoyl esters in the most active dendrimers provides evidence for a hydrophobic component in substrate binding, which is absent in a closely related, less active diastereomeric peptide dendrimer.