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Sixth Topic

Sixth Topic. Diseases of. Amino Acid Metabolism. The following appeared in the Health Section of The Washington Post on July 2, 2002. Treatment Restrict exposure to triggering substances Penicillin Oral doses of thyroid hormone. Early replacement of missing hormones

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Sixth Topic

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  1. Sixth Topic Diseases of Amino Acid Metabolism

  2. The following appeared in the Health Section of The Washington Post on July 2, 2002

  3. Treatment Restrict exposure to triggering substances Penicillin Oral doses of thyroid hormone Early replacement of missing hormones Special diet low in phenylalanine started soon after birth Prevention of prolonged fasting Eliminate dairy products Oral biotin supplements Special diet, and in some cases, liver transplant Special diet Special diet and supplements

  4. Review the diseases of urea synthesis

  5. Metabolic Diseases of the Urea Cycle carbamoylphosphate synthetase carbamoylphosphate ornithine transcarbamoylase ornithine citrulline argininosuccinate synthetase arginase argininosuccinate arginine argininosuccinate lyase

  6. Calcium oxalate is one cause of kidney stones

  7. PHENYLKETONURIA

  8. The three alternative causes of PKU Tyrosine hydroxylase THB DHB DHB reductase TetrahydrobiopterinDihydrobiopterin GTP is precursor

  9. Tyrosine hydroxylase PHE TYR DHB reductase All three defects cause phenylketonuria (PKU) of varying degrees of severity. The symptoms are the excretionin urine of phenylpyruvate, phenyllactate, and/or phenylacetate Tetrahydrobiopterin GTP is precursor

  10. Treatment for PKU The major cause of PKU Tyrosine hydroxylase Loss of enzyme--no cure. Dietary treatment PHE TYR THB DHB Administering reduced biopterin sometimes helps DHB reductase Tetrahydrobiopterin Treat by administering biopterin GTP is precursor

  11. Disease: PKU--phenylketonuria If not treated PKU causes severe mental retardation. All states and the district screen babies at birth. As the brain develops it gradually becomes possible to switch to a normal diet. What would you think would be in this synthetic diet? 1. Thecarbon skeleton of phenylalanine replaces phenylalanine 2. Extra tyrosine to replace that which would normally come from phenylalnine

  12. The diagnostic urinary metabolites of PKU

  13. DISEASES OF TYROSINE METABOLISM TYROSINEMIA I AND II ALKAPTONURIA

  14. TYROSINEMIA II

  15. Tyrosine Tyrosine transaminase homogentisate Disease: tyrosinemia II Oculocutaneous tyrosinemia: eye and skin lesions, mental retardation

  16. ALKAPTONURIA

  17. Tyrosine Tyrosine transaminase homogentisate homogentisate oxidase Disease: alkaptonuria Homogentisate is excreted in urine, and turns black when exposed to air. This disease is the first known described inborn error of metabolism, and a great example of “nole ne nocere”.

  18. TYROSENEMIA I

  19. Tyrosine This is a very serious disease. It results in liver and kidney complications; maleylacetoacetate and fumarylacetate are alkylating agents, and can alkylate DNA and cause tumors. Tyrosine transaminase homogentisate homogentisate oxidase maleylacetoacetate Disease: Tyrosinemia I fumarylacetate Hepatorenal tyrosinemia:

  20. Parkinson’s Disease A loss of cells in the substantia negra that synthesize dopamine

  21. A treatment for Parkinson’s disease is L-DOPA. This is Then metabolized in situ to dopamine. Dopamine cannot Be used because it does not cross the blood-brain barrier.

  22. Parkinson’s Disease

  23. One of the three biopterin dependent enzymes Tyrosine hydroxylase

  24. Diagnosis of a biopterin deficiency is possible by looking in the urine for very low, or non-existent, amounts of degradative metabolites of dopamine, epinephrine, nor-epinephrine, and serotonin (also dependent on biopterin for synthesis)

  25. Albinism Also caused by copper deficiency

  26. HOMOCYSTEINURIA • B6 deficiency • B12 or folate deficiency • 3. Enzyme deficiency Homocysteinuria is linked to atherogenesis through a mechanism involving oxidation of lipid plaques

  27. B6 DEFICIENCY CYSTATHIONASE DEFICIENCY

  28. B6 B6 B6

  29. B12 OR FOLATE DEFICIENCY

  30. B12

  31. Deficiency in neonatal period causes retardation. Infant formula is fortified with taurine

  32. A deficiency in hypusine can lead to problems in translation (eIF-4D)

  33. A diet deficient in trp (e.g. dependent on corn for a starch) can lead to pellagra

  34. Diagnostic for B6 deficiency B6

  35. The third biopterin requiring enzyme

  36. MAPLE SYRUP URINE DISEASE Excreted metabolites smell like maple syrup. The disease is usually connected to severe retardation.

  37. Excrete the -keto- acids formed from valine, isoleucine, and leucine Maple syrup urine disease

  38. A biotin deficiency affects the metabolism of leucine. resulting in the excretion of -methylcrotonic acid (urine smells like a cat’s). A deficiency in the carboxylase enzyme Has the same effect.

  39. From leucine Biotin

  40. METABOLISM OF PROPIONYL COA BIOTIN DEFICIENCY---EXCRETION OF PROPIONIC ACID B12 DEFICIENCY—EXCRETION OF METHYLMALONIC ACID ACIDOSIS

  41. Biotin B12

  42. DIAGNOSIS OF FOLATE DEFICIENCY

  43. FIGLU excreted in urine Folate

  44. Achoo!

  45. Scenario: you are asked to supply a 24-hour urine sample. You are lucky enough to have a date with a new and wonderful person. Things turn out even better than expected. Are you really going to collect urine in that bottle before you go to bed? Can you miss this once (or twice) without the doctor noticing?

  46. Better be honest. The doctor can tell whether the sample is really a 24 hour output by looking at how much creatinine is in the sample Creatinine is excreted at a rate dependent on muscle mass

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