Amino acids metabolism summary PDF

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amino acid metabolism summary ...

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Amino acids

Amino acid metabolism notes

Sources of amino acids    

Digestion of proteins in the intestine. Degradation of proteins within the cell. * Many cellular proteins are constantly degraded and resynthesized (turnover). Damaged or unneeded proteins are marked for destruction by the covalent attachment of chains of a small protein, ubiquitin. Polyubiquitinated proteins are subsequently degraded by a large, ATP-dependent complex called the proteasome.

Amino acid Glucogenic and non essential 1-glycine

Synthesis from Serine

CO2 and H2O

2- serine

Enzyme

catabolism

drivatives

Serine hydroxymethyl transferase 1 Need THF

By glycine synthase: the major pathway for glycine Catabolism

Proteins Pyruvate methylene THF (source for one carbon moiety). Creatine

Glycine synthase (glycine cleavage)

Glyoxylate

Glycine transaminase

threonine

threonine aldolase Serine hydroxymethyl transferase 1 Need THF

Glycine

3phosphoglyce rate

3- alanine

Pyruvate

4- Cysteine

Serine source of the carbon and -1 nitrogen Methionine provides the sulphur From Cystine

3phosphoglycerate dehydrogenase Phosphosrine phosphatase

ALT alanine aminotransferase

By amino acid oxidase (oxidative deamination By serine hydroxymethyltransferase to serine which is converted to pyruvate.

pyruvate, the carbon skeleton of cysteine ceramide ethanolamine phospholipids Conversion to pyruvate by (lipotropic factor) a source for one carbon moiety Serine-2 dehydratase OH is a site of Covalent reaction ( Non- oxidative modification of -7 enzyme (deamination activity; as in glycogen synthase, glycogen phosphorylase and hormone .sensitive lipase Pyruvate which can be Oxidized to CO2, H2O and energy. Converted to glucose Alanine-pyruvate shuttle Conversion to glycine, then, it is cleaved -1 to CO2 & NH3

By Cysteine sulfinate (direct oxidative pathway) is the major pathway

Cystine reductase

By cysteine desulfhydrase , direct .deamination By direct transamination

Proteins Pyruvate thioethanolamine, which is a component of CoASH and ACP Taurine precursor of bile salts Synthesis of Cystine formation of disulfide bonds thiol group of cystiene forms the active site of many enzyms. active sulfate (PAPS) Glutathione

Error

Deficient enzyme Or defect in

Accumulated symptoms substance

notes

Primary hyperoxaluria

Enzymes that catabolize glyoxylate. defect in renal tubular reabsorption of glycine glycine cleavage system. defect in the renal reabsorptive mechanism of 4 amino acids: Cystine, lysine arginine, and ornithine. defective carrier mediated - . transport of cystine

glyoxylate.

Defect in glycine metabolism

Maple syrup urine disease (MSUD)

Branched Chain αKeto Acid Dehydrogenase

Homocystinuria

cystathionine synthase

High concentrations of branched chain keto acids in urine high levels of plasma methionine

Cystathioninuria

cystathionase

Phenylketonuria (PKU)

phenylalanine hydroxylase or *dihydrobiopterin reductase.

Glycinuria:

Hyperglycinemia: Cystinuria

Cystinosis: (Cystine Storage Disease

Glycine in urine

Glycine in blood 4 amino acids: Cystine, lysine arginine, and ornithine. In urina

Cystine stones are formed in the renal tubules

Cystine is deposited, as crystals in tissues - and organs

rare lysosomal disorder causing damage of the affected organ. The patient may die from renal. failure) Defect in isoleucine, leucine and valine catabolism

excretion of large amounts of cystathionine in urine increased levels of: phenylacetic acid, phenylpyruvic acid and phenyllactic acid in blood and

Characteristic odour of urine

mental retardation, thrombosis, osteoporosis and dislocated lens

Excretion of methionine, Sadenosyl methionine and homocysteine in urine

Mental retardation. Eczema of the skin. Mousy odour of urine. Hypopigmentation as a result of decreased melanin

increased plasma phenylalanine levels (>20 mg/dl) (normal: 0.7 – 4 mg/dl) ferric chloride test which gives a

urine

pigment fair skin and hair and blue eyes.

Arthritis and generalized pigmentation of connective - (tissue (Ochronosis)

Alkaptonuria

homogentisate oxidase

Accumulation of homogentisate in blood and urine

Tyrosinaemia or tyrosinosis Hepatorenal type (Type I

fumaryl acetoacetate hydrolase.

high levels of plasma .tyrosine

Oculocutaneous type (Type II)

hepatic tyrosine transaminase

Neonatal tyrosinemia

defective phydroxy phenyl pyruvate hydroxylase Tyrosinase enzyme

Albinism Hypomelanosis, Albino

Hartnup disease

blue-green colour with urine. Treatment diet low in phenylalanine and rich in tyrosine darkening of urine on standing in air

Death usually occurs early from liver failure Treatment is by low tyrosine and phenylalanine - .diet

white colour of skin and make it sensitive to light that may lead to burn and carcinoma. - Lack of pigments in hair causing fair hair, and lack of pigments in the eyes causeing photophobia Intestinal absorption of neutral amino acids is impaired Renal tubular reabsorption of neutral amino acids is also impaired impairment of tryptophan absorption

pheochromocytom a (tumour of the adrenal medulla)

Vanillyl mandelic (VMA) is the principal metabolite of epinephrine and norepinephrine, it is excreated in urine. High level in that tumor

used as a diagnostic marker for this tumour...