Nonstandard Aminoacids1

8/12/2019 Nonstandard Aminoacids1

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Non-standard Aminioacids


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Non-standard Amino acids:

Are they abnormal amino acids?

Are they unusual amino acids?

1 .Protein forming amino acids - 20 amino acids

Posttranscriptional modification

2. Non-standard Amino acids

(A) Non-protein amino acids

Function -Structural

FunctionAs a metabolite

As a regulator of metabolic activities

(B) D amino acid


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Protein phosphorylation is widely exploited in DNA damage

repair, signal transduction, cell growth and cell cycle regulation;

The cascades of downstream signals can be triggered by grabbing a

certain phosphoprotein .

Elucidating the characteristics of phosphopeptide recognition is

fundamental to study cellular functions .


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The phosphoproteins are usually classified into two families,

phosphotyrosine(pTyr)-containing and

phosphoserine (pSer)/phosphothreonine (pThr)-containingsequences .

They are phosphorylatedand dephosphorylatedby different

categories of kinases(e.g., pThr/pSer kinase and pThr kinase) and

phosphatases .

Recent studies discovered a few modular domains that particularly

recognizepThr/pSer- or pThr-containing sequences, such as the

breast-cancer-associated protein BRCA1 C-terminal (BRCT)repeats, WW domain and forkhead-associated (FHA) domain .


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Phosphorylation and sulfation

Some of the tyrosine residues can be taggedwith a phosphate

group by protein kinases.It is referred to as phosphotyrosine.

Tyrosine phosphorylation is considered to be one of the key

steps in signal transduction and regulation of enzymatic activity.

Phosphotyrosine can be detected through specific antibodies.

Tyrosine residues may also be modified by the addition of a

sulfate group, a process known as tyrosine sulfation.

Tyrosine sulfation is catalyzed by tyrosylprotein sulfotransferase

(TPST).


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Phosphoserineis an esterof

serineand phosphoric acid

catalyzed by various types ofkinases.

Phosphoserine is a component

of many proteins as the result of

posttranslational modificaations.

Phosphorylation of proteins on

serine and threonine residues

has traditionally been viewed as

a means to allosterically regulatecatalytic activity.

PhosphoserineModifications, like

phosphorylation: A common

mechanism for controlling the

behavior of a protein,;

For eg. activating or inactivating

an enzyme.
http://en.wikipedia.org/wiki/Esterhttp://en.wikipedia.org/wiki/Serinehttp://en.wikipedia.org/wiki/Phosphoric_acidhttp://en.wikipedia.org/wiki/Kinasehttp://en.wikipedia.org/wiki/Phosphorylationhttp://en.wikipedia.org/wiki/Phosphorylationhttp://en.wikipedia.org/wiki/Kinasehttp://en.wikipedia.org/wiki/Phosphoric_acidhttp://en.wikipedia.org/wiki/Serinehttp://en.wikipedia.org/wiki/Ester


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Phosphothreonine

The threonine residue is susceptible to

numerous post-traslational modifications.

The hydroxy side-chain can undergo O-

linked glycosilation.

In addition, threonine residues undergo

phosphorylationthrough the action of a

threonine kinase.

In its phosphorylated form, it can bereferred to as phosphothreonine.


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4-hydroxyproline: Found in plant cell wall

proteins; Synthesized in plant cells in response to

stress.

Hydroxyproline and Hydroxylysine are found in

collagen, a fibrous protein of connective tissues.Found in capillaries, bone and cartilage.

Proline and lysine are formed in the procollagen

and It is hydroxylated in the presence of ascorbic

acid. These hydroxylation help in the cross linkingof the collagen molecules and thereby stabilizing

structure of collagen.

Among these uncommon amino acids are 4-hydroxyproline, a derivative of

proline, and 5-hydroxylysine, derived from lysine.


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Another important uncommon amino

acid is -carboxyglutamate, found in

(1) bloodclotting protein prothrombin

and in(2) certain proteins that bind Ca2 as

part of their biological function.

6-N Methyllysine

is a constituent of myosin, a contractile protein of muscle.


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Elastinis a proteinin connective tissue

that is elasticand allows many tissues in

the body to resume their shape after

stretching or contracting. Elastin helps

skin to return to its original position whenit is poked or pinched. Elastin is also an

important load-bearing tissue in the

bodies of vertebrates.

In humans, elastin is encoded by the ELN

gene.This desmosineis responsible for the

rubber like properties of elastin.

Desmosine is a complex molecule; It isa derivative of four Lys

residues, and is found in the fibrous protein elastin.
http://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Connective_tissuehttp://en.wikipedia.org/wiki/Elasticity_(physics)http://en.wikipedia.org/wiki/Genehttp://en.wikipedia.org/wiki/Genehttp://en.wikipedia.org/wiki/Elasticity_(physics)http://en.wikipedia.org/wiki/Connective_tissuehttp://en.wikipedia.org/wiki/Protein


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Selenocysteine is a special case.

This rare amino acid residue is introduced

during protein synthesis.

Actually derived from serine,

selenocysteine is a constituent of just a

few known proteins.

Selenocysteine has a structure similar tothat of cysteine, but with an atom of

seleniumtaking the place of the usual

sulfur, forming a selenolgroup which is

deprotonated at physiological pH.

Proteins that contain one or more

selenocysteine residues are called

selenoproteins.

Solenocysteine (21-Sec -U)

Pyrrolysine (22Pyl -O)

Present in several Enzymes

(for example glutathione

peroxidases,

tetraiodothyronine 5'

deiodinases, thioredoxin

reductases, formate

dehydrogenases, glycinereductases, selenophosphate

synthetase 1, methionine-R-

sulfoxide reductase B1

(SEPX1), and some

hydrogenases)
http://en.wikipedia.org/wiki/Cysteinehttp://en.wikipedia.org/wiki/Seleniumhttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Glutathione_peroxidasehttp://en.wikipedia.org/wiki/Glutathione_peroxidasehttp://en.wikipedia.org/wiki/Tetraiodothyronine_5_deiodinasehttp://en.wikipedia.org/wiki/Tetraiodothyronine_5_deiodinasehttp://en.wikipedia.org/wiki/Thioredoxin_reductasehttp://en.wikipedia.org/wiki/Thioredoxin_reductasehttp://en.wikipedia.org/wiki/Formate_dehydrogenasehttp://en.wikipedia.org/wiki/Formate_dehydrogenasehttp://en.wikipedia.org/wiki/Glycine_reductasehttp://en.wikipedia.org/wiki/Glycine_reductasehttp://en.wikipedia.org/wiki/Selenophosphate_synthetase_1http://en.wikipedia.org/wiki/Selenophosphate_synthetase_1http://en.wikipedia.org/wiki/SEPX1http://en.wikipedia.org/wiki/Hydrogenasehttp://en.wikipedia.org/wiki/Hydrogenasehttp://en.wikipedia.org/wiki/SEPX1http://en.wikipedia.org/wiki/Selenophosphate_synthetase_1http://en.wikipedia.org/wiki/Selenophosphate_synthetase_1http://en.wikipedia.org/wiki/Selenophosphate_synthetase_1http://en.wikipedia.org/wiki/Selenophosphate_synthetase_1http://en.wikipedia.org/wiki/Selenophosphate_synthetase_1http://en.wikipedia.org/wiki/Glycine_reductasehttp://en.wikipedia.org/wiki/Glycine_reductasehttp://en.wikipedia.org/wiki/Glycine_reductasehttp://en.wikipedia.org/wiki/Formate_dehydrogenasehttp://en.wikipedia.org/wiki/Formate_dehydrogenasehttp://en.wikipedia.org/wiki/Formate_dehydrogenasehttp://en.wikipedia.org/wiki/Thioredoxin_reductasehttp://en.wikipedia.org/wiki/Thioredoxin_reductasehttp://en.wikipedia.org/wiki/Thioredoxin_reductasehttp://en.wikipedia.org/wiki/Tetraiodothyronine_5_deiodinasehttp://en.wikipedia.org/wiki/Tetraiodothyronine_5_deiodinasehttp://en.wikipedia.org/wiki/Tetraiodothyronine_5_deiodinasehttp://en.wikipedia.org/wiki/Tetraiodothyronine_5_deiodinasehttp://en.wikipedia.org/wiki/Glutathione_peroxidasehttp://en.wikipedia.org/wiki/Glutathione_peroxidasehttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Seleniumhttp://en.wikipedia.org/wiki/Cysteine


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N-Methylarginineis an inhibitorof nitric oxide synthase.

Chemically, it is a methylderivative of the amino acidarginine.It is used as a biochemical tool in the study of physiological

role of nitric oxide.

Nitric oxide transient in its function.
http://en.wikipedia.org/wiki/Enzyme_inhibitorhttp://en.wikipedia.org/wiki/Nitric_oxide_synthasehttp://en.wikipedia.org/wiki/Methylhttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Argininehttp://en.wikipedia.org/wiki/Argininehttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Methylhttp://en.wikipedia.org/wiki/Nitric_oxide_synthasehttp://en.wikipedia.org/wiki/Nitric_oxide_synthasehttp://en.wikipedia.org/wiki/Enzyme_inhibitor


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Nitric oxide, also known as nitrogen monoxide, is a moleculewith

chemical formulaNO. It is a free radical.

In mammals including humans, NO is an important cellular signaling

moleculeinvolved in many physiological and pathological processes.

It is a powerful vasodilatorwith a short half-life of a few seconds in the

blood. (Dissection)

Long-known pharmaceuticals like nitroglycerineand amyl nitritewere

discovered, more than a century after their first use in medicine, to be

active through the mechanism of being precursors to nitric oxide.

Low levels of nitric oxide production are important in protecting organs

such as the liver from ischemic damage.
http://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Free_radicalhttp://en.wikipedia.org/wiki/Signaling_moleculehttp://en.wikipedia.org/wiki/Signaling_moleculehttp://en.wikipedia.org/wiki/Nitroglycerinehttp://en.wikipedia.org/wiki/Amyl_nitritehttp://en.wikipedia.org/wiki/Ischemic_damagehttp://en.wikipedia.org/wiki/Ischemic_damagehttp://en.wikipedia.org/wiki/Amyl_nitritehttp://en.wikipedia.org/wiki/Nitroglycerinehttp://en.wikipedia.org/wiki/Signaling_moleculehttp://en.wikipedia.org/wiki/Signaling_moleculehttp://en.wikipedia.org/wiki/Free_radicalhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Molecule


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Acetyllysine(or acetylated lysine) is an acetyl-derivative of the

amino acidlysine. There are multiple forms of acetyllysine .

In proteins, the acetylationof lysine residues is an important

mechanism of epigenetics.

It functions by regulating the binding of histonesto DNAinnucleosomesand thereby controlling the expression of genes

on that DNA.

Non-histone proteins are acetylated as well.

Histone acetyltransferases(HATs) catalyze the addition of acetylgroups from acetyl-CoAonto certain lysine residues of histones

and non-histone proteins.

Histone deacetylases(HDACs) catalyze the removal of acetyl

groups from acetylated lysines.
http://en.wikipedia.org/wiki/Acetylhttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Lysinehttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Acetylationhttp://en.wikipedia.org/wiki/Histonehttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Nucleosomehttp://en.wikipedia.org/wiki/Histone_acetyltransferaseshttp://en.wikipedia.org/wiki/Acetyl-CoAhttp://en.wikipedia.org/wiki/Histone_deacetylaseshttp://en.wikipedia.org/wiki/Histone_deacetylaseshttp://en.wikipedia.org/wiki/Histone_deacetylaseshttp://en.wikipedia.org/wiki/Histone_deacetylaseshttp://en.wikipedia.org/wiki/Acetyl-CoAhttp://en.wikipedia.org/wiki/Acetyl-CoAhttp://en.wikipedia.org/wiki/Acetyl-CoAhttp://en.wikipedia.org/wiki/Histone_acetyltransferaseshttp://en.wikipedia.org/wiki/Histone_acetyltransferaseshttp://en.wikipedia.org/wiki/Histone_acetyltransferaseshttp://en.wikipedia.org/wiki/Nucleosomehttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Histonehttp://en.wikipedia.org/wiki/Acetylationhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Lysinehttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Acetyl


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Non-protein aminoacids:

Some 300 additional amino acids have been found in cells.

They have a variety of functions but are not constituents of

proteins.

Ornithine and citrulline deserve special note because they

are key intermediates (metabolites) in the biosynthesis of

arginine and in the urea cycle .


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Citrulline is made from ornithineand carbamoyl phosphatein one ofthe central reactions in the urea cycle.

Function

Although citrulline is not coded for by DNA directly, several proteins areknown to contain citrulline as a result of a posttranslational modification.

These citrulline residues are generated by a family of enzymes called

peptidylarginine deiminases (PADs);

which convert arginine into citrulline in a process called citrullination ordeimination.

Proteins that normally contain citrulline residues include myelin basic

protein(MBP), filaggrin,and several histoneproteins,;

whereas other proteins, such as fibrinand vimentinare susceptible to

citrullination during cell death and tissue inflammation.
http://en.wikipedia.org/wiki/Ornithinehttp://en.wikipedia.org/wiki/Carbamoyl_phosphatehttp://en.wikipedia.org/wiki/Myelin_basic_proteinhttp://en.wikipedia.org/wiki/Myelin_basic_proteinhttp://en.wikipedia.org/wiki/Filaggrinhttp://en.wikipedia.org/wiki/Histonehttp://en.wikipedia.org/wiki/Fibrinhttp://en.wikipedia.org/wiki/Vimentinhttp://en.wikipedia.org/wiki/Inflammationhttp://en.wikipedia.org/wiki/Inflammationhttp://en.wikipedia.org/wiki/Vimentinhttp://en.wikipedia.org/wiki/Fibrinhttp://en.wikipedia.org/wiki/Histonehttp://en.wikipedia.org/wiki/Filaggrinhttp://en.wikipedia.org/wiki/Myelin_basic_proteinhttp://en.wikipedia.org/wiki/Myelin_basic_proteinhttp://en.wikipedia.org/wiki/Carbamoyl_phosphatehttp://en.wikipedia.org/wiki/Carbamoyl_phosphatehttp://en.wikipedia.org/wiki/Carbamoyl_phosphatehttp://en.wikipedia.org/wiki/Ornithine


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Patients with rheumatoid arthritis often have detectable

antibodies against proteins containing citrulline.

Although the origin of this immune response is not known,

detection of antibodies reactive with citrulline (anti-

citrullinated protein antibodies) containing proteins or

peptides is now becoming an important help in the diagnosis

of rheumatoid arthritis.

In recent studies, citrulline has been found to relax blood

vessels.

Circulating citrulline concentration is, in humans, a biomarker

of intestinal functionality
http://en.wikipedia.org/wiki/Anti-citrullinated_protein_antibodyhttp://en.wikipedia.org/wiki/Anti-citrullinated_protein_antibodyhttp://en.wikipedia.org/wiki/Rheumatoid_arthritishttp://en.wikipedia.org/wiki/Rheumatoid_arthritishttp://en.wikipedia.org/wiki/Rheumatoid_arthritishttp://en.wikipedia.org/wiki/Rheumatoid_arthritishttp://en.wikipedia.org/wiki/Anti-citrullinated_protein_antibodyhttp://en.wikipedia.org/wiki/Anti-citrullinated_protein_antibodyhttp://en.wikipedia.org/wiki/Anti-citrullinated_protein_antibodyhttp://en.wikipedia.org/wiki/Anti-citrullinated_protein_antibodyhttp://en.wikipedia.org/wiki/Anti-citrullinated_protein_antibody


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Citrulline in the form of citrulline malateis sold as aperformance-enhancing athletic dietary supplement, which was

shown to reduce muscle fatigue in a preliminary clinical trial.

The rind of watermelon(Citrullus lanatus) is a good natural

source of citrulline.
http://en.wikipedia.org/wiki/Malic_acidhttp://en.wikipedia.org/wiki/Dietary_supplementhttp://en.wikipedia.org/wiki/Watermelonhttp://en.wikipedia.org/wiki/Watermelonhttp://en.wikipedia.org/wiki/Dietary_supplementhttp://en.wikipedia.org/wiki/Malic_acid


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L-Ornithine is one of the products of the action of the enzymearginaseon L-arginine, creating urea.

Ornithine is a central part of the urea cycle,

Ornithine is recycled and, in a manner, is a catalyst.

Ornithine is not an amino acid coded for by DNA.

However, in mammalian non-hepatic tissues, the main use of the

urea cycle is in arginine biosynthesis,;

so, as an intermediate in metabolic processes, ornithine is quite

important.
http://en.wikipedia.org/wiki/Arginasehttp://en.wikipedia.org/wiki/Argininehttp://en.wikipedia.org/wiki/Ureahttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Ureahttp://en.wikipedia.org/wiki/Argininehttp://en.wikipedia.org/wiki/Arginase


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Ornithine,via the action of ornithine decarboxylase(E.C.4.1.1.17), is the starting point for the synthesis of polyaminessuch

as putrescine.

In bacteria, such as E. coli, ornithine can be synthesized from L-

glutamate.

Ornithine is also the starting point for cocainebiosynthesis, when

decarboxylased, then modified greatly by Cytochrome P450.
http://en.wikipedia.org/wiki/Ornithine_decarboxylasehttp://en.wikipedia.org/wiki/Polyaminehttp://en.wikipedia.org/wiki/Putrescinehttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Glutamic_acidhttp://en.wikipedia.org/wiki/Glutamic_acidhttp://en.wikipedia.org/wiki/Cocainehttp://en.wikipedia.org/wiki/Cytochrome_P450http://en.wikipedia.org/wiki/Cytochrome_P450http://en.wikipedia.org/wiki/Cytochrome_P450http://en.wikipedia.org/wiki/Cytochrome_P450http://en.wikipedia.org/wiki/Cocainehttp://en.wikipedia.org/wiki/Glutamic_acidhttp://en.wikipedia.org/wiki/Glutamic_acidhttp://en.wikipedia.org/wiki/Glutamic_acidhttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Putrescinehttp://en.wikipedia.org/wiki/Polyaminehttp://en.wikipedia.org/wiki/Ornithine_decarboxylasehttp://en.wikipedia.org/wiki/Ornithine_decarboxylasehttp://en.wikipedia.org/wiki/Ornithine_decarboxylase


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Potential medical uses

Exercise fatigue

L-Ornithine supplementation attenuated fatigue in subjects in a placebo controlled study

using a cycle ergometer. The results suggested that L-ornithine has an antifatigue effect in

increasing the efficiency of energy consumption and promoting the excretion of

ammonia.

Stress

L-Ornithine reduced stress in mice and made them more sociable toward other mice as

well as the scientists conducting the experiment.

Cirrhosis

L-ornithine-L-aspartate (LOLA), a stable salt of ornithine and aspartic acid, has been used

in the treatment of cirrhosis.

Weightlifting supplement

Amino acidsupplements, including L-ornithine, are frequently used by body-builders and

weightlifters to increase levels of HGH. In a Finnish study, these supplements, in low

doses, were not found to increase levels of growth hormone.

However, the study did notadminister the amino-acids while the subjects were fasting, an important requirement in

testing for the effect of amino acids on HGH stimulation.
http://en.wikipedia.org/wiki/Hepatic_encephalopathyhttp://en.wikipedia.org/wiki/Cirrhosishttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/HGHhttp://en.wikipedia.org/wiki/HGHhttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Cirrhosishttp://en.wikipedia.org/wiki/Hepatic_encephalopathy


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D-Aminoacids:

Post-translational modifications:

Modification involves conversion of amino acids in

peptide linkage the L- fprm to D-configurations.

Isolated from amphibians, snails and invertebrates.


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Peptides with D amino acids:

Bacterial peptides contain D- amino acids;

Eg. Tyrocidines and Gramicidin-S

These are by multi enzyme complex synthesis without the

participation of m-RNA.

Peptide bond with D-amino acids resist to proteases.


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D-amino acid containing peptides from Frog:

Dermorphin: Heptapeptide:

Tyr-D-Ala- Phe-Gly-Tyr-Pro-Ser amide

-Lys-

-Asn-

Deltrophin:

Tyr-D-Met-Phe-His-Leu-Met-Asp- amide

D-Ala Asp

D-Ala Glu

D-Alanine in

Dermorphin was

discovered when it was

found that the synthetic

peptide with the same

sequence of L-amino

acid was biologically

inactive.


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Frog: Bombicines: A group of antibacterial peptides;

D-allo-isok=leucines

Snail:Achatin I : Gly-D-Phe-Ala- Asp.

This regulates the muscle contraction.

Unusual aminoacids in peptide bonds:

Carnosinecontains -Alanine

Glutathionecontains gamma carboxy bond.


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Non-standard amino acids that are found in proteins are formed by

post-translational modification, which is modification after translation during protein

synthesis. These modifications are often essential for the function or regulation of a

protein; for example, the carboxylationof glutamateallows for better binding of

calcium cations,[38]and the hydroxylationof prolineis critical for maintaining

connective tissues.[39]

Another example is the formation of hypusinein thetranslation initiation factorEIF5A, through modification of a lysine residue.[40]Such

modifications can also determine the localization of the protein, e.g., the addition of long

hydrophobic groups can cause a protein to bind to a phospholipid membrane.[41]
http://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/Post-translational_modificationhttp://en.wikipedia.org/wiki/Carboxylationhttp://en.wikipedia.org/wiki/Glutamatehttp://en.wikipedia.org/wiki/Calcium_in_biologyhttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Hydroxylationhttp://en.wikipedia.org/wiki/Prolinehttp://en.wikipedia.org/wiki/Collagenhttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Hypusinehttp://en.wikipedia.org/wiki/Eukaryotic_initiation_factorhttp://en.wikipedia.org/wiki/EIF5Ahttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/File:Beta_alanine_comparison.pnghttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/EIF5Ahttp://en.wikipedia.org/wiki/Eukaryotic_initiation_factorhttp://en.wikipedia.org/wiki/Hypusinehttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Collagenhttp://en.wikipedia.org/wiki/Prolinehttp://en.wikipedia.org/wiki/Hydroxylationhttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Calcium_in_biologyhttp://en.wikipedia.org/wiki/Calcium_in_biologyhttp://en.wikipedia.org/wiki/Glutamatehttp://en.wikipedia.org/wiki/Carboxylationhttp://en.wikipedia.org/wiki/Post-translational_modificationhttp://en.wikipedia.org/wiki/Post-translational_modificationhttp://en.wikipedia.org/wiki/Post-translational_modification


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Some nonstandard amino acids are not found in proteins. Examples include

lanthionine, 2-aminoisobutyric acid, dehydroalanine, and the neurotransmitter

gamma-aminobutyric acid. Nonstandard amino acids often occur as intermediates

in the metabolic pathwaysfor standard amino acids for example, ornithineand

citrullineoccur in the urea cycle, part of amino acid catabolism(see below).[42]A

rare exception to the dominance of -amino acids in biology is the -amino acid

beta alanine(3-aminopropanoic acid), which is used in plants and microorganisms

in the synthesis of pantothenic acid(vitamin B5), a component of coenzyme A
http://en.wikipedia.org/wiki/Lanthioninehttp://en.wikipedia.org/wiki/2-aminoisobutyric_acidhttp://en.wikipedia.org/wiki/Dehydroalaninehttp://en.wikipedia.org/wiki/Gamma-aminobutyric_acidhttp://en.wikipedia.org/wiki/Metabolic_pathwayhttp://en.wikipedia.org/wiki/Ornithinehttp://en.wikipedia.org/wiki/Citrullinehttp://en.wikipedia.org/wiki/Urea_cyclehttp://en.wikipedia.org/wiki/Catabolismhttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Beta_alaninehttp://en.wikipedia.org/wiki/Pantothenic_acidhttp://en.wikipedia.org/wiki/Coenzyme_Ahttp://en.wikipedia.org/wiki/Coenzyme_Ahttp://en.wikipedia.org/wiki/Pantothenic_acidhttp://en.wikipedia.org/wiki/Pantothenic_acidhttp://en.wikipedia.org/wiki/Pantothenic_acidhttp://en.wikipedia.org/wiki/Beta_alaninehttp://en.wikipedia.org/wiki/Beta_alaninehttp://en.wikipedia.org/wiki/Amino_acidhttp://en.wikipedia.org/wiki/Catabolismhttp://en.wikipedia.org/wiki/Urea_cyclehttp://en.wikipedia.org/wiki/Citrullinehttp://en.wikipedia.org/wiki/Ornithinehttp://en.wikipedia.org/wiki/Metabolic_pathwayhttp://en.wikipedia.org/wiki/Gamma-aminobutyric_acidhttp://en.wikipedia.org/wiki/Gamma-aminobutyric_acidhttp://en.wikipedia.org/wiki/Gamma-aminobutyric_acidhttp://en.wikipedia.org/wiki/Gamma-aminobutyric_acidhttp://en.wikipedia.org/wiki/Gamma-aminobutyric_acidhttp://en.wikipedia.org/wiki/Dehydroalaninehttp://en.wikipedia.org/wiki/2-aminoisobutyric_acidhttp://en.wikipedia.org/wiki/2-aminoisobutyric_acidhttp://en.wikipedia.org/wiki/2-aminoisobutyric_acidhttp://en.wikipedia.org/wiki/Lanthionine

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Nonstandard Aminoacids1