WBR1018
| Author | [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry |
| Sub Category | SubCategory::General Principles |
| Prompt | [[Prompt::A 5- month old boy was brought by the parents to the hospital with complaints of poor feeding and growth, hypotonia, lactic acidemia, and mild acidosis. The ratio of pyruvate to lactate in serum is elevated and there is decreased conversion of pyruvate to acetyl CoA in fibroblast. Which of the following compounds would most likely benefit this patient?]] |
| Answer A | AnswerA::Pyridoxine |
| Answer A Explanation | AnswerAExp::Pyridoxine also known as vitamin B6 is not required in the pyruvate dehydrogenase complex. It is used in transamination (eg ALT and AST), decarboxylation reactions and glycogen phosphorylase. |
| Answer B | AnswerB::Thiamine |
| Answer B Explanation | AnswerBExp::Correct. See explanation. |
| Answer C | AnswerC::Cobalamin |
| Answer C Explanation | AnswerCExp::Cobalamin, also known as Vitamin B12 is a cofactor for homocysteine methyltransferase and methylmalonyl-CoA mutase. It is not required in the pyruvate dehydrogenase complex. |
| Answer D | AnswerD::Biotin |
| Answer D Explanation | AnswerDExp::Biotin is also known, as Vitamin B7 and it is a cofactor for carboxylation enzymes and not required in the pyruvate dehydrogenase complex. |
| Answer E | AnswerE::Ascorbic acid |
| Answer E Explanation | AnswerEExp::Ascorbic acid is also known as Vitamin C, necessary for hydroxylation of proline and lysine in collagen synthesis. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::An elevation of pyruvate and deficiency of acetyl CoA suggest a deficiency of pyruvate dehydrogenase, which requires thiamine (Vitamin B1), one of the cofactors in the pyruvate dehydrogenase complex. Findings include neurologic deficits, usually starting in infancy. Other cofactors include Vitamins B2 (Riboflavin or FAD+), B3 (Niacin or NAD+), B5 (CoA or Pantothenate) and Lipoic acid.
MNEUMONIC: Tender Loving Care For Nancy (Thiamine, Lipoic acid, CoA, FAD+, NAD+).
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| Approved | Approved::Yes |
| Keyword | WBRKeyword::Pyruvate dehydrogenase |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |