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==What is Lysine?==

==What is Lysine?==

Lysine is an '''essential amino acid for dogs and cats'''. Lysine is classified as a '''ketogenic''' amino acid and contains a long, positively charged side chain. Dietary lysine is absorbed by a dibasic amino acid transporter in the small intestine (particularly the [[:Category:Small Intestine - Anatomy & Physiology|jejunum]]) and plasma lysine is actively reabsorbed in the proximal tubule of the [[:Category:Kidney - Anatomy & Physiology|kidney]].

Lysine is an '''essential amino acid for dogs and cats'''. Lysine is classified as a '''ketogenic''' amino acid and contains a long, positively charged side chain. Dietary lysine is absorbed by a dibasic amino acid transporter in the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] (particularly the [[:Category:Small Intestine - Anatomy & Physiology|jejunum]]) and plasma lysine is actively reabsorbed in the proximal tubule of the [[:Category:Kidney - Anatomy & Physiology|kidney]].

==Why is it Important?==

==Why is it Important?==

Lysine and lysine-containing compounds, such as hydroxylysine found in collagen; '''play an important role in the secondary structure of [[Protein Overview - Nutrition|proteins]]'''; the positively charged side chain is used for binding to other molecules, such as DNA during replication; and lysine acetylation also plays a role in regulating cellular metabolism<ref name="NRC">National Research Council (NRC). Protein and Amino Acids. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p. 125-126.</ref><ref>Zhao S, et al. Regulation of cellular metabolism by lysine acetylation. Science 2010;327:1000-1004.</ref>.

Lysine and lysine-containing compounds, such as hydroxylysine found in collagen; '''play an important role in the secondary structure of [[Protein Overview - Nutrition|proteins]]'''; the positively charged side chain is used for binding to other molecules, such as DNA during replication; and lysine acetylation also plays a role in regulating cellular metabolism<ref name="NRC">National Research Council (NRC). Protein and Amino Acids. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p. 125-126.</ref><ref>Zhao S, et al. Regulation of cellular metabolism by lysine acetylation. Science 2010;327:1000-1004.</ref>.

Inherited defects in the transporter for dibasic amino acids can result in poor absorption of lysine (as well as the other dibasic amino acids cystine, ornithine, and [[Arginine - Nutrition|arginine]]) from the intestinal mucosa and poor reabsorption of plasma lysine in the renal tubule<ref>Hoppe A, et al. Urinary excretion of amino acids in normal and cystinuric dogs. Br Vet J 1993;149:253-68.</ref>.

Inherited defects in the transporter for dibasic amino acids can result in poor absorption of lysine (as well as the other dibasic amino acids cystine, ornithine, and [[Arginine - Nutrition|arginine]]) from the intestinal mucosa and poor reabsorption of plasma lysine in the [[Nephron Microscopic Anatomy#Proximal Tubule|renal tubule]]<ref>Hoppe A, et al. Urinary excretion of amino acids in normal and cystinuric dogs. Br Vet J 1993;149:253-68.</ref>.

==Roles in the Body==

==Roles in the Body==

Lysine plays a key role in determining the secondary structure of proteins. It is a precursor of hydroxylysine, a key component of collagen, and of carnitine, which plays an important role in energy metabolism by transporting fatty acids into the mitochondria. Lysine can be de-aminated by intestinal bacterial to form the foul-smelling compound cadaverine<ref name="NRC"/>.

Lysine plays a key role in determining the secondary structure of proteins. It is a precursor of hydroxylysine, a key component of collagen, and of carnitine, which plays an important role in energy metabolism by transporting fatty acids into the mitochondria. Lysine can be de-aminated by intestinal bacterial to form the foul-smelling compound cadaverine<ref name="NRC"/>.

====Cats:====  

====Cats:====  

Lysine antagonises arginine induced promotion of herpes virus in vitro<ref>Maggs DJ, et al. Effects of L-lysine and L-arginine on in vitro replication of feline herpesvirus type-1. AJVR 2000;61:1474-1478.</ref>, and oral supplementation (400 mg PO q 24h to 500 mg PO q 12h) has been shown to decrease both viral shedding and severity of conjunctivitis in herpes virus-infected cats<ref>Maggs DJ, et al. Efficacy of oral supplementation with L-lysine in cats latently infected with feline herpesvirus. AJVR 2003;64:37-42.</ref><ref>Stiles J, et al. Effect of oral administration of L-lysine on conjunctivitis caused by feline herpesvirus in cats. AJVR 2002;63:99-103.</ref>. However other studies<ref>Maggs DJ, et al. Effects of dietary lysine supplementation in cats with enzootic upper respiratory disease. J Fel Med Surg 2007;9:97-108.</ref><ref>Drazenovich T, et al. Effects of dietary lysine supplementation on upper respiratory and ocular disease and detection of infectious organisms in cats within an animal shelter. AJVR 200;70:1391-400.</ref> have not shown an effect of lysine supplementation on non-ophthalmological herpes virus, [[Chlamydophila felis|Chlamydophila]], or [[Feline Calicivirus|calicivirus]] shedding or on the severity of upper respiratory infection signs.

Lysine antagonises arginine induced promotion of herpes virus in vitro<ref>Maggs DJ, et al. Effects of L-lysine and L-arginine on in vitro replication of feline herpesvirus type-1. AJVR 2000;61:1474-1478.</ref>, and oral supplementation (400 mg PO q 24h to 500 mg PO q 12h) has been shown to decrease both viral shedding and severity of conjunctivitis in [[Feline Herpesvirus 1|herpes virus]]-infected cats<ref>Maggs DJ, et al. Efficacy of oral supplementation with L-lysine in cats latently infected with feline herpesvirus. AJVR 2003;64:37-42.</ref><ref>Stiles J, et al. Effect of oral administration of L-lysine on conjunctivitis caused by feline herpesvirus in cats. AJVR 2002;63:99-103.</ref>. However other studies<ref>Maggs DJ, et al. Effects of dietary lysine supplementation in cats with enzootic upper respiratory disease. J Fel Med Surg 2007;9:97-108.</ref><ref>Drazenovich T, et al. Effects of dietary lysine supplementation on upper respiratory and ocular disease and detection of infectious organisms in cats within an animal shelter. AJVR 200;70:1391-400.</ref> have not shown an effect of lysine supplementation on non-ophthalmological herpes virus, [[Chlamydophila felis|Chlamydophila]], or [[Feline Calicivirus|calicivirus]] shedding or on the severity of upper respiratory infection signs.

==Consequences of Lysine Deficiency==

==Consequences of Lysine Deficiency==

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