Catalyzes the deimination of arginine residues of proteins. H2O + L-arginyl-[protein] = L-citrullyl-[protein] + NH4(+) Binding of Ca(2+) triggers a conformation change that is essential for catalytic activity. Homodimer. Expressed in various tissues including muscle, uterus, spinal cord, salivary gland and pancreas. Expressed during the estrus cycle. Expressed during diestrus and proestrus with an eight fold decline when estrus cycle is reached. Belongs to the protein arginine deiminase family.