Examining Arginase-1 Trimerization Uncovers a Promising Allosteric Site for Inhibition

Arginase-1 (ARG-1) is a promising target for cancer immunotherapy, but the small size and the highly polar nature of its catalytic site present significant challenges for inhibitor development. An alternative strategy to induce enzyme inhibition by targeting protein oligomerization has been developed recently, offering several advantages such as increased selectivity, promotion of protein degradation, and potential substoichiometric inhibition. In this study, we demonstrated that only trimeric ARG-1 is active, which was confirmed by producing monomeric arginase-1. Through in silico-driven site-directed mutagenesis, we identified an allosteric site involving five key amino acids responsible for ARG-1 trimerization. We further demonstrated the covalent modification of a key arginine residue within this pocket using phenylglyoxal disrupted ARG-1 oligomerization. Although phenylglyoxal has limited potency, it effectively supports the concept of ARG-1 inhibition via homomeric disruption, validating this allosteric targeting approach.