enzymology An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

, a protein-arginine deiminase (PAD) () is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that

catalyzes Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

a form of

post translational modification In molecular biology, post-translational modification (PTM) is the covalent process of changing proteins following protein biosynthesis. PTMs may involve enzymes or occur spontaneously. Proteins are created by ribosomes, which translate mRNA in ...

called arginine de-imination or

citrullination Citrullination or deimination is the conversion of the amino acid arginine in a protein into the amino acid citrulline. Citrulline is not one of the 20 standard amino acids encoded by DNA in the genetic code. Instead, it is the result of a post-tr ...

: :protein L-arginine + H₂O

\rightleftharpoons

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

products Product may refer to: Business * Product (business), an item that can be offered to a market to satisfy the desire or need of a customer. * Product (project management), a deliverable or set of deliverables that contribute to a business solution ...

are protein L-citrulline and NH₃: : This enzyme belongs to the family of

hydrolase In biochemistry, hydrolases constitute a class of enzymes that commonly function as biochemical catalysts that use water to break a chemical bond: :\ce \quad \xrightarrowtext\quad \ce This typically results in dividing a larger molecule into s ...

s, those acting on carbon-nitrogen bonds other than

peptide bond In organic chemistry, a peptide bond is an amide type of covalent chemical bond linking two consecutive alpha-amino acids from C1 (carbon number one) of one alpha-amino acid and N2 (nitrogen number two) of another, along a peptide or protein cha ...

s, specifically in linear

amidine Amidines are organic compounds with the functional group RC(NR)NR2, where the R groups can be the same or different. They are the imine derivatives of amides (RC(O)NR2). The simplest amidine is formamidine, HC(=NH)NH2. Examples of amidines includ ...

s. The

systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature. A semisystematic name or semitrivi ...

of this enzyme class is protein-L-arginine iminohydrolase. This enzyme is also called peptidylarginine deiminase.

Structural studies

As of late 2007, seven

structures A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

have been solved for this class of enzymes, with PDB accession codes , , , , , , and .

Mammalian proteins

Mammals have 5 protein-arginine deiminases, with symbols * PADI1, PADI2, PADI3,

PADI4 Protein-arginine deiminase type-4, is a human protein which in humans is encoded by the ''PADI4'' gene. The protein as an enzyme, specifically protein-arginine deiminase, a type of hydrolase. Molecular biology The human gene is found on the sh ...

, PADI6 except for

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s, there the letter case is different: *Padi1, Padi2, Padi3, Padi4, Padi6 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, YW3-56 Reversible inhibitors * GSK484, GSK199

References

* * EC 3.5.3 Enzymes of known structure {{3.5-enzyme-stub