Tagged: Histidine

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Histidine to histamine conversion

Histamine causes vasodilatation and bronchoconstriction. In the stomach it stimulates the secretion of hydrochloric acid (HCl). Histamine binds to H1 receptors in the stomach, stimulating the release of gastric acid. Pharmacological blockers of H1 receptors are used in the treatment of gastric reflux. H2 receptors are located on basophils; histamine stimulates their degranulation during the allergic responses. H2 receptor blockers are used to treat allergic conditions. Histamine is produced from Histidine by: A. Deamination B. Transamination C. Carboxylation D. Decarboxylation E. Methylation The correct answer is D- Decarboxylation. Histamine is a biogenic amine. A biogenic amine is a potent signaling...

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Case study- Hyperammonemia

Question of the day -Hyperammonemia A new-born becomes progressively lethargic after feeding. His respiratory rate increases and he becomes virtually comatose, responding only to painful stimuli, and exhibits mild respiratory alkalosis. Suspicion of a urea cycle disorder is aroused and evaluation of serum amino acid levels is initiated. In the presence of hyperammonemia, production of which of the following amino acids is always increased? A. Glycine B. Arginine C. Proline D. Histidine E. Glutamine Answer- The correct answer is Glutamine. Urea cycle disorder results in reduced ammonia disposal and hence the patients present with symptoms of hyperammonemia. Ammonia is detoxified by...

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Answer- Case study- Oral contraceptives induced vitamin deficiencies

Case Details Oral contraceptives are known to lower blood levels of folate and vitamin B6. Which of the following conversion processes might be directly affected? A. Ornithine to Citrulline B. Histidine to histamine C. Glutamate to Glutamine D. Propionyl co A to Methyl malonyl co A E. Phenyl alanine to Tyrosine Answer- B- The correct answer is conversion of Histidine to histamine. The reaction is catalyzed by decarboxylase that requires B6-P as a cofactor (Figure-1) that gets deficient in women upon long-term oral contraceptive usage. Folic acid is not required in this reaction. Figure-1- Decarboxylation of Histidine is carried out...

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Answer- Case study- Hartnup disease- A 28- year-old man complains of a rash on his sun- exposed skin, diarrhea and loss of balance..

A 28- year-old man complains of a rash on his sun- exposed skin, diarrhea and loss of balance. His urinalysis results are significant for an increase in neutral amino acids. The patient is diagnosed with Hartnup’s disease that occurs due to a defective transport of neutral amino acids in the kidney. Apart from tryptophan which of the following amino acids would have been found in urine? A. Lysine B. Arginine C. Histidine D. Phenyl alanine E. Glutamic acid Answer The right option is D- Phenyl alanine. Hartnup disease is an autosomal recessive disorder caused by impaired neutral (i.e., mono amino...

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Case study- Hartnup’s disease- A 28- year-old man complains of a rash on his sun exposed skin, diarrhea and ..

22/01/2014 Amino acid chemistry QUESTION OF THE DAY A 28- year-old man complains of a rash on his sun exposed skin, diarrhea and loss of balance. His urinalysis results are significant for an increase in neutral amino acids. The patient is diagnosed with Hartnup’s disease that occurs due to  defective transport of neutral amino acids in the kidney. Apart from tryptophan which of the following amino acids would have been found in urine? A. Lysine B. Arginine C. Histidine D. Phenyl alanine E. Glutamic acid Figure- Patient with hartnup disease showing pellagra like rashes For answer- Follow the link http://usmle.biochemistryformedics.com/answer-case-study-hartnup-disease-a-28-year-old-man-complains-of-a-rash-on-his-sun-exposed-skin-diarrhea-and-loss-of-balance/...

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