Nitrogen Metabolism Flashcards
Sources of amino acid pool (3)
Turnover of body protein
Dietary intake
Synthesis of non-essential AA
2 main steps in removing nitrogen from AA
Transamination
Oxidative Deamination
AA transferred to a-ketoglutarate in transamination to form glutamate except: (2)
Lysine
Threonine
Transamination enzyme and co-enzyme?
Aminotransferases; Pyridoxal phosphate (B6)
In transamination, pyruvate interconvert with?
Alanine
In transamination, aspartate interconvert with?
Oxaloacetate
Transamination vs oxidative deamination:
Occurs in all cell of the body
No free ammonia
Transamination
Transamination vs oxidative deamination:
Occurs in the liver and kidney?
Only for glutamate
Liberates ammonia
Oxidative deamination
Glutamate + Ammonia?
Enzyme?
Glutamine
Glutamine Synthetase
Glucose-Alanine Cycle
Pyruvate + Glutamate = ?
Enzyme?
Alanine aminotransferase (ALT/SGPT)
Deaminates glutamine to produce ammonium ion which is excreted from the body.
Glutaminase
Glutaminase is present where?
Small intestine
Kidney
Urea cycle is present only in:
Liver
Substrates of Urea Cycle (3)
NH3 from
Aspartate
CO2
Steps in Urea Cycle (8)
Ornithine Carbamoyl Phosphate Citrulline Aspartate Arginosuccinate Fumarate Arginine Urea
(Old Colorful Cats Are Also Fussing About Urea)
Urea Cycle Enzymes:
Formation of carbamoyl phosphate
Carbamoyl phosphate synthetase I
Urea Cycle Enzymes:
Formation of citrulline
Ornithine transcarbamoyolase
Urea Cycle Enzymes:
Synthesis of Arginosuccinate
Arginosuccinate Synthetase
Urea Cycle Enzymes:
Cleavage of Arginosuccinate to form arginine
Argininosuccinase
Urea Cycle Enzymes:
Arginine cleavage to form urea and ornithine
Arginase
Urea Cycle Enzymes:
Rate Limiting Step and Enzyme?
CO2 + NH3 –> Carbamoyl phosphate
CPS I
Urea Cycle Enzymes:
Energy Requirement
4 moles of ATP
Urea Cycle Enzymes:
Cofactors
N-acetylglutamate
Biotin
Hereditary hyperammonemia
Type 1
Carbamoyl phosphate synthetase I
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