Protein-arginine deiminase

In enzymology, a protein-arginine deiminase (PAD) (EC 3.5.3.15) is an enzyme that catalyzes a form of post translational modification called arginine de-imination or citrullination:

protein L-arginine + H₂O ${\displaystyle \rightleftharpoons }$ protein L-citrulline + NH₃

protein-arginine deiminase
Protein-arginine deiminase 4, dimer, Human
Identifiers
EC no.	3.5.3.15
CAS no.	75536-80-0
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

Thus, the two substrates of this enzyme are protein L-arginine (arginine residue inside a protein) and H₂O, whereas its two products are protein L-citrulline and NH₃:

This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in linear amidines. The systematic name of this enzyme class is protein-L-arginine iminohydrolase. This enzyme is also called peptidylarginine deiminase.

Structural studies

As of late 2007, seven structures have been solved for this class of enzymes, with PDB accession codes 1WD8, 1WD9, 1WDA, 2DEW, 2DEX, 2DEY, and 2DW5.

Mammalian proteins

Mammals have 5 protein-arginine deiminases, with symbols

• PADI1, PADI2, PADI3, PADI4,^[1] PADI6^[2]

except for rodents, there the letter case is different:

• Padi1, Padi2, Padi3, Padi4, Padi6^[3]

The different case is just a historical artifact. It doesn't indicate that the rodent proteins are special.

Inhibitors

Irreversible inhibitors

• Cl-amidine, BB-Cl-Amidine,^[4] YW3-56^[5]

Reversible inhibitors

• GSK484, GSK199