Abstract
Seven mutant forms of human phosphomannomutase 2 were produced in Escherichia coli and purified. These mutants had a Vmax of 0.2-50% of the wild enzyme and were unstable. The least active protein (R141H) bears a very frequent mutation, which has never been found in the homozygous state whereas the second least active protein (D188G) corresponds to a mutation associated with a particularly severe phenotype. We conclude that total lack of phosphomannomutase 2 is incompatible with life. Another conclusion is that the elevated residual phosphomannomutase activity found in fibroblasts of some patients is contributed by their mutated phosphomannomutase 2.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Substitution
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Cloning, Molecular
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Congenital Disorders of Glycosylation / enzymology*
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Congenital Disorders of Glycosylation / genetics*
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Enzyme Stability
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Escherichia coli
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Fibroblasts / enzymology
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Genotype
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Homozygote
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Hot Temperature
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Humans
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Kinetics
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Mutagenesis, Site-Directed
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Phosphotransferases (Phosphomutases) / chemistry
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Phosphotransferases (Phosphomutases) / genetics*
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Phosphotransferases (Phosphomutases) / metabolism*
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Point Mutation*
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Recombinant Proteins / chemistry
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Recombinant Proteins / metabolism
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Thermodynamics
Substances
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Recombinant Proteins
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Phosphotransferases (Phosphomutases)
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phosphomannomutase