Insights into matriptase-2 substrate binding and inhibition mechanisms

Matriptase-2 belongs to the family of type II transmembrane serine proteases, representing an emerging class of cell surface proteolytic enzymes, and is predominantly expressed in the liver [1]. Physiologically, matriptase-2 was identified to be a key regulator in iron homeostasis. Mutations of the gene encoding matriptase-2 were linked to iron-refractory iron deficiency anemia [2, 3]. It was shown that matriptase-2 suppresses the expression of hepcidin [3, 4], the main regulator of systemic iron homeostasis, through cleavage of the bone morphogenetic protein co-receptor hemojuvelin [5]. Due to the important role of matriptase-2 in iron homeostasis, the enzyme represents a novel target for the development of inhibitors, potentially useful in the treatment of hemochromatosis or beneficial as pharmacological tools.

To investigate the interaction of matriptase-2 with prototype low-molecular weight ligands, site-directed mutagenesis, kinetic analysis and molecular modeling studies were performed. A peptidic substrate [1] and matriptase-2 inhibitors from a previous work [6] were chosen to perform an active site scan of matriptase-2. In our study, we could explore the importance of several active site amino acids in substrate/enzyme and inhibitor/enzyme interactions and identify residues that enhanced (Phe⁶⁶⁵) or reduced (Asp⁷⁸⁵, Tyr⁷¹²) the affinity of peptide ligands.