An Update on Arginase Inhibitors and Inhibitory Assays

Arginase, which converts arginine into ornithine and urea, is a promising therapeutic target. Arginase is involved in cardiovascular diseases, parasitic infections and, through a critical role in immunity, in some cancers. There is a need to develop effective arginase inhibitors and therefore efforts to identify and optimize new inhibitors are increasing. Several methods of evaluating arginase activity are available, but few directly measure the product. Radiometric assays need to separate urea and dying reactions require acidic conditions and sometimes heating. Hence, there are a variety of different approaches available, and each approach has its own limits and benefits. In this review, we provide an update on arginase inhibitors, followed by a discussion on available arginase assays and alternative methods, with a focus on the intrinsic biases and parameters that are likely to impact results.

New cinnamid and rosmarinic acid derived compounds biosynthesized in Escherichia coli as Leishmania amazonensis arginase inhibitors

Arginase is a metalloenzyme that plays a central role in Leishmania infection. Previously, rosmarinic and caffeic acids were described as antileishmanial and as a Leishmania amazonensis arginase inhibitor and now, we describe the inhibition of arginase in L. amazonensis by rosmarinic acid analogs (1-7) and new caffeic acids derived amides (8-10). Caffeic acid esters and amides were produced by means of the engineered synthesis in E. coli and tested against L. amazonensis arginase. New amides (8-10) were biosynthesized in E. coli cultured with 2 mM of different combinations of feeding substrates. The most potent arginase inhibitors showed Ki(s) between 2 - 5.7 μM. Compounds 2-4 and 7 inhibited L-ARG through a noncompetitive mechanism, and 9 showed a competitive inhibition. By applying an in silico protocol we determined the binding mode of compound 9. The competitive inhibitor of L-ARG targets key residues within the binding site of the enzyme establishing a metal coordination bond with the metal ions as well as a series of hydrophobic and polar contacts supporting its micromolar inhibition of L-ARG. These results highlight that the dihydroxycinnamic-derived compounds can be used as the basis for the development of new drugs using a powerful tool based on the biosynthesis of arginase inhibitors.