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what is phenylketonuria
- occurs in newborns when they lack the enzyme (phenylalanine hydroxylase) to convert amino acid phenylalanine to tyrosine.
- phenylalanin is toxic to brain cells and accumulates in the blood
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amino acid in an acid pH will have what charge?
+
-
amino acid in a basic pH will have what charge?
-
-
what is the zwitterion form of an amino acid
- dipolar form
- contains both + and - charge
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what are the amino acids humans can't synthesize
- leu
- ile
- val
- met
- phe
- trp
- thr
- lys
- his
- arg
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enzyme defects affected by tyrosine aminoacidopathy and how is it tested?
- enzyme defects: FAAH, TAT, 4- HPPO
- test: mass spec
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PAH enzyme defect leads to what aminoacidopathy and how is it tested?
- aminoacidopathy: PKU
- test: mass spec, BIA
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what aminoacidopathy is called by enzyme defect of HGO
alkaptonuria
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what are the 3 screening newborns for PKU?
- BIA (bacterial inhibition assay)
- fluorometric analysis
- mass spec
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describe BIA
- incorporating B. subtilis spores in an agar plate with B-theinylalanine. B-theinylalanine is a metabolic inhibitor to B. subtilis growth. A filter disc with blood is placed on agar. A growth would occur if the phenylalanine exceeds the range of 2-4 mg/dL.
- Phenylalanine counteracts the antagonist and allows growth to occur
- produce a lot of false positives
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how is fluorescence used to screen for PKU?
- using the fluorescence of phenylalanine ninhydrin copper in the presence of dipeptide
- produce fewer false positives than BIA
-
how is mass spec used to obtain phenylalanine and tyrosine levels
- using the ratio between phe/tyr to determine the phe levels
- produce fewer false positives than BIA
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