Amino Acids Overview - Nutrition

Overview

Amino acids are the structural components of proteins in all plants, animals and fungi. Amino acids are considered either indispensable (essential) and dispensable (non-essential). Essential amino acids are those that are required pre-formed in the diet as the animal either lacks the metabolic pathway to synthesise the given amino acid or is unable to make sufficient quantities for growth and normal physiologic/biochemical functions. Non-essential amino acids are those that can be produced endogenously from available nitrogen and carbon sources. There are nine essential amino acids required by humans which are: methionine; lysine; phenylalanine; histidine; threonine; tryptophan; and the branched-chain amino acids, leucine, isoleucine, and valine. In addition to these 9 amino acids, dogs also have a requirement for arginine. Cats have a requirement for the same essential amino acids as the dog, plus the amino-sulfonic acid taurine.

In addition to their structural role in proteins, amino acids can be utilized as energy substrates during periods of fasting or starvation. Amino acids are able to provide a carbon skeleton for either glucose production or synthesise ketone bodies, or both.

• Exclusively gluconeogenic amino acids:
  • arginine
  • histidine
  • methionine (+ cysteine)
  • threonine
  • valine
• Strictly ketogenic:
  • leucine
  • lysine
• Both gluconeogenic and ketogenic:
  • isoleucine
  • phenylalanine (+ tyrosine)
  • thryptophan

Amino acids are also important components of biologically active compounds such as the neurotransmitters serotonin and catecholamine’s, nucleotides, nitric oxide and many others.

Additional Reading

1. National Research Council (NRC). Protein and Amino Acids. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p.111-120.
2. Case LP, et al. Protein Requirements. In Canine and Feline Nutrition: A resource for Companion Animal Professionals. 2011 Third Ed. St. Louis: Mosby p.95-106.