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Publication Abstract from PubMed

Inhibitors of the human enzyme dimethylarginine dimethylaminohydrolase-1 (DDAH1) can control endogenous nitric oxide production. A time-dependent covalent inactivator of DDAH1, N(5)-(1-imino-2-chloroethyl)-l-ornithine ( KI = 1.3 muM, kinact = 0.34 min(-1)), was conceptually dissected into two fragments and each characterized separately: l-norvaline ( Ki = 470 muM) and 2-chloroacetamidine ( KI = 310 muM, kinact = 4.0 min(-1)). This analysis suggested that the two fragments were not linked in a manner that allows either to reach full affinity or reactivity, prompting the synthesis and characterization of three analogues: two that mimic the dimethylation status of the substrate, N(5)-(1-imino-2-chloroisopropyl)-l-ornithine ( kinact /KI = 208 M(-1) s(-1)) and N(5)-(1-imino-2-chlorisopropyl)-l-lysine ( kinact /KI = 440 M(-1) s(-1)), and one that lengthens the linker beyond that found in the substrate, N(5)-(1-imino-2-chloroethyl)-l-lysine (Cl-NIL, KI = 0.19 muM, kinact = 0.22 min(-1)). Cl-NIL is one of the most potent inhibitors reported for DDAH1, inactivates with a second order rate constant (1.9 x 10(4) M(-1) s(-1)) larger than the catalytic efficiency of DDAH1 for its endogenous substrate (1.6 x 10(2) M(-1) s(-1)), and has a partition ratio of 1 with a >100000-fold selectivity for DDAH1 over arginase. An activity-based protein-profiling probe is used to show inhibition of DDAH1 within cultured HEK293T cells (IC50 = 10 muM) with cytotoxicity appearing only at higher concentrations (ED50 = 118 muM). A 1.91 A resolution X-ray crystal structure reveals specific interactions made with DDAH1 upon covalent inactivation by Cl-NIL. Dissecting a covalent inactivator and analysis of its constituent fragments proved useful for the design and optimization of this potent and effective DDAH1 inhibitor.

Dissection, Optimization, and Structural Analysis of a Covalent Irreversible DDAH1 Inhibitor.,Burstein-Teitelbaum G, Er JAV, Monzingo AF, Tuley A, Fast W Biochemistry. 2018 Jul 20. doi: 10.1021/acs.biochem.8b00554. PMID:29983043^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.