Year: 2025
Type: article
Abstract: Human ADP-ribosyltransferase 1 ( hs ART1, EC: 2.4.2.31) is a membrane-associated GPI-anchored, arginine-specific, mono-ADP-ribosyltransferase. The enzyme resides on the endoplasmic reticulum and extracellular cell surface, where it catalyzes the transfer of ADP-ribose (ADPR) from NAD + to arginine residues of neighboring target proteins, forming free nicotinamide (NAM) and N-linked mono-ADP-ribosylation (MARylation) of the target protein. Arginine-specific MARylation regulates the target’s function and cellular roles. Dysregulation of hs ART1 activity has been shown to permit immune cell evasion in non-small cell lung cancer (NSCLC). Inhibition of hs ART1 decreases tumor efficacy and increases T-cell infiltration. hs ART1 is an emerging checkpoint target in select cancers. We performed the first kinetic characterization of the ADP-ribosyltransferase and NAD + glycohydrolase activities of hs ART1. Without an l -arginine substrate, hs ART1 slowly hydrolyses NAD + into NAM and ADPR through an ordered kinetic mechanism. NAD + binding and hydrolysis are followed by the ordered release of NAM followed by ADPR. The ADP-ribosyltransferase activity of hs ART1 to l -arginine-like small molecule substrates gives over a 100-fold improvement in k cat / K m and k cat relative to NAD + hydrolysis. With ADP-ribose acceptors, hs ART1 proceeds through a partially ordered mechanism, whereby the substrate binding of NAD + and l -arginine-like substrate is random. Chemistry proceeds through a ternary complex, and product release is ordered, with NAM first, followed by the ADP-ribosylated acceptor. hs ART1 is not diffusionally rate-limited on k cat and only partially limited on k cat / K m for l -arginine methyl ester. The detailed description of the kinetic mechanism of hs ART1 can aid in the development of novel and selective inhibitors.
Source: Biochemistry
Authors: Daniel P. Groom, Amanda Lopacinski, Scott J. Garforth, Vern L. Schramm
Institution: Albert Einstein College of Medicine
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W4409738982