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Vitamin B6-responsive and -unresponsive cystathioninuria: two variant molecular forms
Science (New York, N.Y.)
|December 19, 1975
Summary
Vitamin B6 responsive cystathioninuria showed increased cystathionase activity with pyridoxal phosphate. This enzyme was immunochemically identical to normal cystathionase, unlike in B6 unresponsive cases.
Area of Science:
- Biochemistry
- Genetics
- Metabolic Disorders
Background:
- Cystathioninuria is a rare metabolic disorder.
- Vitamin B6 is a crucial cofactor for enzymes involved in amino acid metabolism.
- The specific enzyme defect in cystathioninuria is not always clear.
Purpose of the Study:
- To investigate the activity and immunochemical properties of cystathionase in vitamin B6-responsive and unresponsive cystathioninuria.
- To determine if pyridoxal phosphate can restore enzyme function in affected cell lines.
Main Methods:
- Enzyme activity assays on lymphoid cell line extracts.
- Pyridoxal phosphate supplementation in vitro.
- Immunodiffusion assays using antiserum to human hepatic cystathionase.
Main Results:
- Cystathionase activity was significantly increased by pyridoxal phosphate in cell extracts from a vitamin B6-responsive patient.
- The cystathionase protein from the responsive patient was immunochemically identical to normal cystathionase.
- No increase in activity or immunochemical identity was observed in cell extracts from a vitamin B6-unresponsive patient.
Conclusions:
- The vitamin B6-responsive form of cystathioninuria may involve a mutation affecting pyridoxal phosphate binding or enzyme conformation.
- Cystathionase is the likely enzyme deficient in this vitamin B6-responsive patient.
- The B6-unresponsive patient may have a different enzymatic defect or a more severe mutation.
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