A little excerpt from Pet Education about arginine:
"Arginine is also an amino acid. Most animals manufacture the amino acid ornithine through various processes, some of which require arginine. In cats, the only method to produce ornithine is to convert it from arginine. Ornithine is necessary because it binds ammonia produced from the breakdown of protein. If cats are deficient in arginine, there will not be enough ornithine to bind the ammonia, and severe signs such as salivation, vocalization, ataxia, and even death can result from the high ammonia levels. These signs often occur several hours after a meal, when most of the ammonia is produced. Although deficiencies are rare, they cat occur in cats who are not eating or have certain liver diseases such as hepatic lipidosis.