Mechanistic studies of protein arginine deiminase 2: evidence for a substrate-assisted mechanism

UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology

Publication Date


Document Type



Biocatalysis; Calcium; Humans; Hydrogen-Ion Concentration; Hydrolases; Isoenzymes; Kinetics; Solvents; Substrate Specificity


Biochemistry | Enzymes and Coenzymes | Medicinal-Pharmaceutical Chemistry | Therapeutics


Citrullination, which is catalyzed by protein arginine deiminases (PADs 1-4 and 6), is a post-translational modification (PTM) that effectively neutralizes the positive charge of a guanidinium group by its replacement with a neutral urea. Given the sequence similarity of PAD2 across mammalian species and the genomic organization of the PAD2 gene, PAD2 is predicted to be the ancestral homologue of the PADs. Although PAD2 has long been known to play a role in myelination, it has only recently been linked to other cellular processes, including gene transcription and macrophage extracellular trap formation. For example, PAD2 deiminates histone H3 at R26, and this PTM leads to the increased transcription of more than 200 genes under the control of the estrogen receptor. Given that our understanding of PAD2 biology remains incomplete, we initiated mechanistic studies on this enzyme to aid the development of PAD2-specific inhibitors. Herein, we report that the substrate specificity and calcium dependence of PAD2 are similar to those of PADs 1, 3, and 4. However, unlike those isozymes, PAD2 appears to use a substrate-assisted mechanism of catalysis in which the positively charged substrate guanidinium depresses the pKa of the nucleophilic cysteine. By contrast, PADs 1, 3, and 4 use a reverse-protonation mechanism. These mechanistic differences will aid the development of isozyme-specific inhibitors.

DOI of Published Version



Biochemistry. 2014 Jul 15;53(27):4426-33. doi: 10.1021/bi500554b. Epub 2014 Jul 3. Link to article on publisher's site

Journal/Book/Conference Title



At the time of publication, Christina Dreyton and Paul Thompson were not yet affiliated with UMass Medical School.

Related Resources

Link to Article in PubMed