IT12 YTR Metabolism of Amino Acid

8/11/2019 IT12 YTR Metabolism of Amino Acid

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METABOLISM AMINO ACID

BY

Yanti Rosita


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The twenty amino acids can be

divided into two groups The Ten "Nonessential" AminoAcids:

Alanine, Asparagine, Aspartate, Cysteine,

Glutamate, Glutamine, Glycine, Proline, Serine

and Tyrosine (synthesized from phenylalanine)

The Ten "Essential" AminoAcids:

Arginine, Histidine, Isoleucine, Leucine, Lysin,

Methionine, Phenylalanine, Threonine,Tryptophan and Valine


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THE CONCEPT OF NITROGEN

BALANCE

Positive nitrogen balance(net protein

synthesis) occurs during growth, pregnancy, or

recuperation from a wasting disease

Negative nitrogen balance(nitrogen

excretion exceeds intake). Occurs during

malnutrition, surgery or severe trauma,

long-term bed rest, or situations of excesscorticosteroid secretion


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Synthesis of Nonessential Amino Acids

Three very common a-ketoacids can be

transaminated in one step to their corresponding

amino acid:

- Pyruvate (glycolytic end product) alanine- Oxaloacetate (citric acid cycle intermediate)

aspartate

- a-ketoglutarate (citric acid cycle intermediate)glutamate


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Synthesis of Nonessential Amino

Acids

Proline, Ornithine and Arginineare derived

from Glutamate

Cysteineis synthesized from serine and

homocysteine

Asparagineand glutamineare synthesized from

aspartate and glutamate by asparagine synthetase

and glutamine synthetase,

Serineis formed from 3-phosphoglycerate,

a glycolysis intermediate


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Synthesis of Nonessential Amino Acids

Tyrosine, can only be made from the essential

amino acid phenylalanine

Glycineis formed from serine, or directly from

CO2, NH4+, and N5,N10-methylenetetrahydrofolate.

Glycine can be made from choline

Hydroxyproline, found in collagen, issynthesized from proline


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Synthesis of Essential Amino

Acids

The synthetic pathways for the essential

amino acids are:

(1) present only in microorgansims

(2) considerably more complex than for

nonessential amino acids

(3) use familiar metabolic precursors

(4) show species variation


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For purposes of classification, consider the

following 4 "families" which are based upon

common precursors:

(1) Aspartate Family: lysine, methionin, threonin

(2) Pyruvate Family: leucine, isoleucine, valine

(3) Aromatic Family: phenylalanine, Tyrosine,

tryptophan

(4) Histidine


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METABOLISM OF AMINO ACID

CARBON CHAINS

amino acid is glucogenicif its carbon skeletoncan be metabolized to citric acid cycle

intermediates or pyruvate Most amino acids are

glucogenic

amino acid is ketogenicif its oxidative degradation

leads to acetyl CoA or intermediates of fatty acid

oxidation. Examples:leucine and lysine

Amino acid is glicoketogenic:

isoleucine, lysine, phenylalanine, tyrosine, and

tryptophan


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All amino acids, exeption of lysine and

threonin can participate in transamination

The most abundant aminotransferases are

alanin-glutamat aminotransferase

(SGPT/ALT) and aspartat glutamat

aminotransferase (SGOT/AST)


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NITROGENOUS COMPOUNDS MADE FROM


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NITROGENOUS COMPOUNDS MADE FROM

AMINO ACIDS

Neurotransmitters- epinephrinand norepinephrinare derived

from tyrosine

- Serotoninis synthesized from tryptophan- histaminis made from histidine

Creatine,

As a storage coumpound of chemical energy

in muscle and brain is synthesized from

glysineand arginine
http://web.indstate.edu/thcme/mwking/aminoacidderivatives.htmlhttp://web.indstate.edu/thcme/mwking/aminoacidderivatives.htmlhttp://web.indstate.edu/thcme/mwking/aminoacidderivatives.htmlhttp://web.indstate.edu/thcme/mwking/aminoacidderivatives.html


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Tryptopan serves as the precursor for the synthesis of

serotonin(5-hydroxytryptamine, 5-HT) and melatonin

(N-acetyl-5-methoxytryptamine).


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ABNORMALITIES IN AMINO ACID

CATABOLISM

Phenylketonuria (PKU)Is caused by an autosomal recessive mutationin the gene or phenylalanine hydroxylase

AlkaptonuriaIs inborn error of tyrosine metabolism. Theenzyme homogentisate is missing

Albinism

A defect in tyrosine oxidase, characterized bythe absence of melanin in skin, hair, retina etc


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IT12 YTR Metabolism of Amino Acid