Nitrogen Metabolism Flashcards by Lyssa Peralta

Sources of amino acid pool (3)

Turnover of body protein
Dietary intake
Synthesis of non-essential AA

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2 main steps in removing nitrogen from AA

Transamination

Oxidative Deamination

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AA transferred to a-ketoglutarate in transamination to form glutamate except: (2)

Lysine

Threonine

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Transamination enzyme and co-enzyme?

Aminotransferases; 
Pyridoxal phosphate (B6)

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In transamination, pyruvate interconvert with?

Alanine

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In transamination, aspartate interconvert with?

Oxaloacetate

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Transamination vs oxidative deamination:
Occurs in all cell of the body
No free ammonia

Transamination

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Transamination vs oxidative deamination:
Occurs in the liver and kidney?
Only for glutamate
Liberates ammonia

Oxidative deamination

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Glutamate + Ammonia?

Enzyme?

Glutamine

Glutamine Synthetase

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Glucose-Alanine Cycle
Pyruvate + Glutamate = ?
Enzyme?

Alanine aminotransferase (ALT/SGPT)

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Deaminates glutamine to produce ammonium ion which is excreted from the body.

Glutaminase

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Glutaminase is present where?

Small intestine

Kidney

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Urea cycle is present only in:

Liver

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Substrates of Urea Cycle (3)

NH3 from
Aspartate
CO2

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Steps in Urea Cycle (8)

Ornithine
Carbamoyl Phosphate
Citrulline
Aspartate
Arginosuccinate
Fumarate 
Arginine
Urea

(Old Colorful Cats Are Also Fussing About Urea)

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Urea Cycle Enzymes:

Formation of carbamoyl phosphate

Carbamoyl phosphate synthetase I

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Urea Cycle Enzymes:

Formation of citrulline

Ornithine transcarbamoyolase

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Urea Cycle Enzymes:

Synthesis of Arginosuccinate

Arginosuccinate Synthetase

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Urea Cycle Enzymes:

Cleavage of Arginosuccinate to form arginine

Argininosuccinase

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Urea Cycle Enzymes:

Arginine cleavage to form urea and ornithine

Arginase

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Urea Cycle Enzymes:

Rate Limiting Step and Enzyme?

CO2 + NH3 –> Carbamoyl phosphate

CPS I

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Urea Cycle Enzymes:

Energy Requirement

4 moles of ATP

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Urea Cycle Enzymes:

Cofactors

N-acetylglutamate

Biotin

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Hereditary hyperammonemia

Type 1

Carbamoyl phosphate synthetase I

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Hereditary hyperammonemia | Type 2

Ornithine transcarbamoylase

Hereditary hyperammonemia | Dx

Hyperammonemia Inc blood glutamine Decreased BUN

Hereditary hyperammonemia | Treatment

Low protein diet Na Benzoate Phenylpyruvate

Acquired hyperammonemia | Sx

``` Tremors Slurring of speech Somnolence Vomiting Blurring of vision Cerebral edema ```

Ketogenic AA

Leucine | Lysine

Ketogenic and Glucogenic

Phenylalanine Tyrosine Tryptophan Isoleucine

Yields of ketogenic AA

Acetoacetate | Acetyl coA

Yields of glucogenic AA

Glucose | Glycogen

``` Entry points: Glutamine Glutamate Proline Arginine Histidine ```

Alpha ketoglutarate

``` Entry points: Alanine Serine Glycine Cysteine Threonine Tryptophan ```

Pyruvate

Entry points: Phenylalanine Tyrosine

Fumarate

``` Entry points: Methionine Valine Isoleucine Threonine ```

Succinyl CoA

Entry points: Aspartate Asparagine

Oxaloacetate

Synthesis of Non Essential Amino Acids | Transamination of alpha ketoacids (3)

Alanine Aspartate Glutamate

Synthesis of Non Essential Amino Acids | Amidation of glutamate and aspartate (2)

Glutamine and asparagine

Synthesis of Non Essential Amino Acids | Synthesized from glutamate

Proline

Synthesis of Non Essential Amino Acids | Made from methionine and serine

Cysteine

Synthesis of Non Essential Amino Acids | Made from 3-phosphoglycerate

Serine

Synthesis of Non Essential Amino Acids | Made from serine

Glycine

Synthesis of Non Essential Amino Acids | Made from phenylalanine

Tyrosine

Raw Material in Biosynthesis: | Heme, purines, creatine, bile acid conjugation

Glycine

Raw Material in Biosynthesis: | Phospholipid & sphingolipid, purines, thymines

Serine

Raw Material in Biosynthesis: | GABA

Glutamine

Raw Material in Biosynthesis: Thioethanolamine of CoA Taurine

Cysteine

Raw Material in Biosynthesis: | Histamine

Histidine

Raw Material in Biosynthesis: | Creatinine, polyamine, NO

Arginine

``` Raw Material in Biosynthesis: Serotonin NAD NADP Melatonin ```

Tryptophan

Raw Material in Biosynthesis: Catecholamine Thyroid hormones Melanin

Tyrosine

Deficiency in phenylketonuria

Decreased phenylalanine hydroxylase | Decreased tetrahydrobiopterine cofactor

Tx in Phenylketonuria

Decreased phenylalanine | Increased tyrosine

Deficiency in alkaptonuria

Homogentisic acid oxidase

Black urine Ochronosis Debilitating arthralgia

Alkaptonuria

Deficient tyrosinase or tyrosine transporters

Albinism

Homocystinuria | Tx for: Cystathione synthase deficiency

Low methionine High cysteine High B6 High folate

``` Sx: Mental retardation Osteoporosis Tall stature Kyphosis Lens subluxation Atherosclerosis (Stroke in the Young) ```

Homocystinuria

Common inherited defect of renal tubular amino acid transporter at PCT of kidneys

Cystinuria

Cystinuria: transporter defect for what proteins?

Cystine Ornithine Lysine Arginine

Tx for cystinuria

Acetazolamide to alkalinaze urine

Deficiency in MSUD

Alpha ketoacid dehydrogenase

Heme Synthesis: Rate limiting step? Enzyme? Cofactor?

Glycine + succinyl coA --> alpha-levulinic acid ALA synthase Pyridoxine

Heme Synthesis: Porphobilinogen formation Enzyme? How many ALA? Cofactor? Inhibited by?

ALA dehydratase Cofactor: Zinc Inhibited by: Heavy metal ions

Heme Synthesis: Heme formation Iron is introduced to: Rate enhanced by: Inhibited by:

Heme formation Iron is introduced to: Protoporphyrin IX Rate enhanced by: Ferrochelatase Inhibited by: Lead

Photosensitivity Abdominal pain Neuropsychiatric symptoms Most common porphyria

Porohyria cutanea tarda

Pyridoxine deficiency with isoniazid therapy

Sideroblastic anemia with ringed sideroblasts

Enzymed inactivated by lead poisoning

ALA Dehydratase | Ferrochelatase

Disease with increased urinary ALA and free erytrocyte porphyrin

Lead poisoning

Enzyme involved: X-linked sideroblastic anemia Sx: Anemia

ALA Synthase (erythroid)

Acute intermittent porphyria Abd pain Neuropsych symptoms Urinary porphobilinogen + Uroporphyrin positive

Uroporphyrinogen I synthase

Congenital erythropoietic No photosensitivity Porphobilinogen negative Uroporphyrin positive

Uroporohyrinogen III synthase

Heme --> biliverdin --> bilirubin Enzyme?

Heme oxygenase

Bilirubin conjugated to bilirubin diglucoronide Enzyme?

Bilirubin diglucuronyltransferase

Deficient in Crigler Najjar I, II, and Gilbert?

Bilirubin diglucuronyltransferase

Rotor Syndrome | Dubin Johnson syndrome

Conjugated hyperbilirubinemia