L-Arginine turnover

Unless otherwise stated all data on this page refer to the human proteins. Gene information is provided for human (Hs), mouse (Mm) and rat (Rn).

Overview

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L-arginine is a basic amino acid with a guanidino sidechain. As an amino acid, metabolism of L-arginine to form L-ornithine, catalysed by arginase, forms the last step of the urea production cycle. L-Ornithine may be utilised as a precursor of polyamines (see Carboxylases and Decarboxylases) or recycled via L-argininosuccinic acid to L-arginine. L-Arginine may itself be decarboxylated to form agmatine, although the prominence of this pathway in human tissues is uncertain. L-Arginine may be used as a precursor for guanidoacetic acid formation in the creatine synthesis pathway under the influence of arginine:glycine amidinotransferase with L-ornithine as a byproduct. Nitric oxide synthase uses L-arginine to generate nitric oxide, with L-citrulline also as a byproduct.

L-Arginine in proteins may be subject to post-translational modification through methylation, catalysed by protein arginine methyltransferases. Subsequent proteolysis can liberate asymmetric NG,NG-dimethyl-L-arginine (ADMA), which is an endogenous inhibitor of nitric oxide synthase activities. ADMA is hydrolysed by dimethylarginine dimethylhydrolase activities to generate L-citrulline and dimethylamine.

2.1.1.- Protein arginine N-methyltransferases

Overview

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Protein arginine N-methyltransferases (PRMT, EC 2.1.1.-) encompass histone arginine N-methyltransferases (PRMT4, PRMT7, EC 2.1.1.125) and myelin basic protein N-methyltransferases (PRMT7, EC 2.1.1.126). They are dimeric or tetrameric enzymes which use S-adenosyl methionine as a methyl donor, generating S-adenosylhomocysteine as a by-product. They generate both mono-methylated and di-methylated products; these may be symmetric (SDMA) or asymmetric (NG,NG-dimethyl-L-arginine) versions, where both guanidine nitrogens are monomethylated or one of the two is dimethylated, respectively.

Enzymes

PRMT1 Show summary »

PRMT2 Show summary »

PRMT3 Show summary »

PRMT4 Show summary »

PRMT5 Show summary »

PRMT6 Show summary »

PRMT7 Show summary »

PRMT8 Show summary »

PRMT9 Show summary »

PRMT10 Show summary »

F-box protein 10 Show summary »

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Arginase

Overview

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Arginase (EC 3.5.3.1) are manganese-containing isoforms, which appear to show differential distribution, where the ARG1 isoform predominates in the liver and erythrocytes, while ARG2 is associated more with the kidney.

Enzymes

ARG1 (Arginase I) Show summary »

ARG2 (Arginase II) Show summary »

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Arginine:glycine amidinotransferase

Enzymes

AGAT (Arginine:glycine amidinotransferase) Show summary »

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Dimethylarginine dimethylaminohydrolases

Overview

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Dimethylarginine dimethylaminohydrolases (DDAH, EC 3.5.3.18) are cytoplasmic enzymes which hydrolyse NG,NG-dimethyl-L-arginine to form dimethylamine and L-citrulline.

Enzymes

DDAH1 (NG,NG-Dimethylarginine dimethylaminohydrolase 1) Show summary »

DDAH2 (NG,NG-Dimethylarginine dimethylaminohydrolase 2) Show summary »

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Nitric oxide synthases

Overview

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Nitric oxide synthases (NOS, E.C. 1.14.13.39) utilise L-arginine (not D-arginine) and molecular oxygen to generate nitric oxide and L-citrulline. The nomenclature suggested by NC-IUPHAR of NOS I, II and III [11] has not gained wide acceptance. eNOS and nNOS isoforms are activated at concentrations of calcium greater than 100 nM, while iNOS shows higher affinity for Ca2+/calmodulin (CALM2, CALM3, CALM1, P62158) and thus appears to be constitutively active. All the three isoforms are homodimers and require sapropterin, flavin adenine dinucleotide, flavin mononucleotide and NADPH for catalytic activity. L-NAME is an inhibitor of all three isoforms, with an IC50 value in the micromolar range.

Enzymes

eNOS (Endothelial NOS) Show summary »

iNOS (Inducible NOS) Show summary »

nNOS (Neuronal NOS) Show summary »

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Further reading

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References

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