Modulating furin activity with designed mini-PDX peptides: Synthesis and in vitro kinetic evaluation

Abstract

A peptide was designed from reactive site loop structure of alpha 1 Antitrypsin Portland known as alpha 1 PDX as a novel mini-PDX inhibitor of furin. The sequence was derived from (367-394) that contains the crucial furin cleavage motif RIPR382. A P3 mutant replacing Ile(380) by Len was prepared as a first model peptide. A Cys residue was inserted at each terminal of the peptide for purpose of cyclisation which was accomplished by air or iodine-induced oxidation. This mini-PDX peptide both cyclic and acyclic form inhibited in vitro furin activity (IC50 in nM) when measured against either substrates Boc-RVRR double down arrow MCA or QVEGF-C vertical bar Abz-QVHSIIRR double down arrow SLP-Y(NO2)-A-CONH2, Abz = 2-amino benzoic acid and Y(NO2) = 3-nitro tyrosine vertical bar, latter being derived from vascular endothelial growth factor-C (VEGF-C) processing site. The geometrically constrained structure mimicking PDX reactive loop is crucial for enzyme inhibition. Our study further revealed that both mini-PDX peptides inactivate furin in a slow tight binding manner, with disulfide-bridged cyclic form being slightly more potent. Unlike PDX, these peptides inhibit furin via a different mechanistic pathway. The study provides an alternate strategy for development of efficient peptide-based inhibitors of Proprotein Convertases including furin.