Methionine is one of the 10-plus essential amino acids that are required by both the cat and dog. It is a non-polar, glucogenic amino acid and, according to the 2006 US National Resource Council (NRC) report, it is typically the first limiting amino acid in cat diets and the first or second limiting amino acid in dog diets.
A partial explanation for its first or second limitation status is due to its ability to donate or receive constituent groups. At the whole-animal level, methionine is part of body proteins and is important for skin and coat condition, eye health, heart health and more. At the metabolic level, methionine is a methyl (CH3) group donor through formation of the co-enzyme S-adenosylmethionine necessary for methyl group transfer. It is a sulfur donor and thereby an indicator of B-vitamin status.
