Taurine and arginine play a key role in the feline diet but I am unaware as to where exactly they fit in.
From the Taurine Wikipedia article:
Arginine is an Essential Amino Acid for cats (and many other mammals - including Humans while we're infants). That is, they cannot synthesize it on their own and must obtain it entirely from their diet. A 10lb. (5kg) cat will require about .86g of Arginine - which is abundant in all meats and can be met with a few ounces of food.
I could not find anything particularly special about Arginine as opposed to other EAA's for cats.