AMINO ACID METABOLISMS
This presentation is the property of its rightful owner.
Sponsored Links
1 / 25

AMINO ACID METABOLISMS PowerPoint PPT Presentation


  • 84 Views
  • Uploaded on
  • Presentation posted in: General

AMINO ACID METABOLISMS. Amino acid structure. Essential amimo acids Val, Leu Ile Phe Met, Thr, Lys, Arg * , Hys * , Trp Non essential amino acids Gly, Ala, Ser, Pro, Hyp 1 , Cys, Tyr, Asn, Gln, Asp, Glu, Hyl 1. AMINO ACID METABOLISM. BODY PROTEINS. Degradation. Proteosynthesis.

Download Presentation

AMINO ACID METABOLISMS

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Amino acid metabolisms

AMINO ACID METABOLISMS


Amino acid metabolisms

Amino acid structure


Amino acid metabolisms

Essential amimo acids

Val, Leu Ile Phe Met, Thr, Lys, Arg*, Hys*, Trp

Non essential amino acids

Gly, Ala, Ser, Pro, Hyp1, Cys, Tyr, Asn, Gln, Asp, Glu, Hyl1


Amino acid metabolisms

AMINO ACID METABOLISM

BODY PROTEINS

Degradation

Proteosynthesis

NONPROTEIN

DERIVATIVES

Porphyrins

Purines

Pyrimidines

Neurotransmitters

Hormones

Komplex lipids

Aminosugars

Digestion

AMINO ACIDS

DIETARY

PROTEINS

GLYCOLYSIS

KREBS CYCLE

Conversion

(Carbon skeleton)

Transamination

UREA

NH3

GLUCOSE CO2KETONBODIES


Amino acid metabolisms

Enzymes cleaving the peptide bonds

Endopeptidases – hydrolyse the peptide bond inside a chain

Pepsin, trypsin, chymotrypsin

Exopeptidases – split the peptide bond at the end of a protein molecule

Aminopeptidase, carboxypeptidases

Dipeptidases

Pepsin (pH 1.5 – 2.5) – peptide bond derived fromTyr, Phe,

bonds between Leu and Glu

Trypsin (pH 7.5 – 8.5) – bonds between Lys a Arg

Chymotrypsin (pH 7.5 – 8.5) – bonds between Phe a Tyr


Amino acid metabolisms

General reactions of amino acids

deamination

a-keto acid

NH2transaminationa-keto acid

+ amino acid

RCH

COOHdecarboxylation amine

General reactions of amino acids are transamination and

deamination of a-amino group

Decarboxylation reaction gives biologically active amines


Amino acid metabolisms

Transamination reactions

The glutamate which is produced by these transaminase reactions is oxidatively deaminated by glutamate dehydrogenase to release ammonium:


Amino acid metabolisms

Transamination reactions

(enzymes aminotransferases)

Transaminases are enzymeswhich transfer the amino groupfrom an amino acid to a keto acid,

usually alpha-ketoglutarate, essentially swapping an amino group with a keto group:

(Alanine-a-ketoglutarate transferase)

another similar reaction yields more common products:

(aspartate-a-ketoglutarate transferase)


Amino acid metabolisms

These reactions are mediated by pyridoxal phosphate (PLP),

a derivative of pyridoxine (vitamin B6):


Amino acid metabolisms

pyridoxal phosphatepyridoxamine phosphate

pyridoxamine phosphate pyridoxal phosphate


Amino acid metabolisms

Clinicaly important transaminases

ALT

Alanine-a-ketoglutarate transferase

Clinical marker for irreversibile liver damage

AST

aspartate-a-ketoglutarate transferase

Clinical marker for irreversibile myocardial damage


Amino acid metabolisms

  • Amino acids with three carbons are converted to pyruvate:

  • Alanine

  • Serine

  • Cysteine

Serine is deaminated by serine dehydratase to form pyruvate + NH4+ in a reaction which doesn't involve the transaminase but does use pyridoxal phosphate (PLP) as a reactive group.

Similarly, threonine can be dehydrated and deaminated to yield pyruvate.

Glycine can be converted to serine for degradation, or it can be cleaved to release CO2, NH4+ and an activated one-carbon unit. In addition, three carbons from tryptophan are converted to pyruvate by way of alanine.


Amino acid metabolisms

Amino acids with three carbons are converted to pyruvate


Amino acid metabolisms

  • Amino acids with five carbons are converted to alpha-ketoglutarate:

  • Arginine

  • Glutamine

  • Histidine

  • Proline

These amino acids are first converted to glutamate which is transaminated to alpha-ketoglutarate.


Amino acid metabolisms

  • Some amino acids are converted to succinyl-CoA:

  • Methionine

  • Valine

  • Isoleucine

These amino acids are converted to propionyl-CoA

which is carboxylated to methylmalonyl-CoA

which is converted to succinyl-CoA.

This last step is an isomerization catalyzed by Methylmalonyl-CoA mutase, an enzyme which uses cobalamin (vitamin B12).


Amino acid metabolisms

Leucine and Lysine are converted to acetyl-CoA and acetoacetate:

Degradation of valine, leucine, and isoleucine requires the oxidative decarboxylation of an alpha-keto acid.

If this enzyme is defective, these acids accumulate in the blood and urine, resulting in maple syrup urine disease (branched chain ketoaciduria).

This disease is characterized by physical and mental retardation.


Amino acid metabolisms

Phenylalanine and Tyrosine are converted to fumarate and acetoacetate

A serious disease results from the inability to oxidize phenylalanine by a defective phenylalanine hydroxylase.

This results in high levels of phenylpyruvate developing (phenylpyruvate is the result of transamination of phenylalanine with an amino acid).

The disease is phenylketonuria (PKU), and results in severe mental retardation and shortens the life span so that half the carriers are dead at 20 and 75% are dead at 30 if it is untreated. It is a genetic disorder and can result from aberrant splicing of the normal phenylalanine hydroxylase transcript.

Therapy for the disease involves restricting the intake of phenylalanine, and must be started immediately after birth. Screening for the disease occurs at birth so that as many effects as possible can be avoided.


Amino acid metabolisms

The twenty common amino acids are degrade to a total of seven different compounds, all of which are related to the citric acid cycle:

Degradation of aminoacids

gives intermediates

for saccharides and lipides synthesis


Amino acid metabolisms

Interconversion of amino acids and intermediates

of carbohydrate metabolism


Amino acid metabolisms

Amino acids

Glucogenicketogenicglucogenic +

ketogenic

Ala HypLeuIle

Arg MetLys

Asp ProPhe

Cys SerTrp

Glu ThrTyr

Glu Val

Gly

His


Amino acid metabolisms

Enzymes which metabolised amino acides

containe vitamines as cofactors

Vater soluble vitamins B

THIAMINE B1 (thiamine diphosphate)

oxidative decarboxylation of a-ketoacids

RIBOFLAVIN B2 (flavin mononucleotide FMN, flavin adenine dinucleotide FAD)

oxidses ofa-aminoacids

NIACIN B3 – nicotinic acid (nikotinamide adenine dinucleotide NAD+

nikotinamide adenine dinukleotide phosphate NADP+)

dehydrogenases, reductase

PYRIDOXIN B6 (pyridoxalphosphate)

transamination reaction and decarboxylation

FOLIC ACID (tetrahydropholate)

Meny enzymes of amino acid metabolism


Amino acid metabolisms

Nitrogenous derivatives of amino acids

Glycine

heme, purine, creatine, conjugation of bile acids

Histidine

histamine

Ornithine a arginin

creatine, polyamines (spermidine, spermine)

Tryptophan

serotonine (melatonine)

Tyrosine

Epinephrine, norepinephrine

Glutamic acid

g-aminobutyric acid (GABA)


Amino acid metabolisms

Aspartame (NutraSweet) consists of a methly ester of L-aspartate and L-phenylalanine:


  • Login