Abstract
A truncated version of human phenylalanine hydroxylase which contains the carboxy terminal 336 amino acids was produced in Escherichia coli. It was purified by ammonium sulfate precipitation, Q-Sepharose chromatography, and hydroxyapatite chromatography. The K(m) values of the truncated enzyme for tetrahydropterin substrates are not different from those of the full-length enzyme, nor are the Vmax values. The KM value for phenylalanine is 2-fold lower for the truncate than for the full-length enzyme. The metal content of the enzyme is 0.27 mol Fe per mole enzyme subunit, and it is activated 2.3-fold by addition of ferrous ion to assays; it is not activated by addition of copper. The truncated enzyme shows no lag in activity when an assay is started with phenylalanine, while the full-length enzyme shows a marked lag.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Binding Sites
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Biopterins / analogs & derivatives
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Biopterins / metabolism
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Catalysis
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Chromatography, High Pressure Liquid
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Copper / analysis
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Copper / pharmacology
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Enzyme Activation
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Escherichia coli / genetics
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Ferrous Compounds / pharmacology
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Humans
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Iron / analysis
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Kinetics
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Phenylalanine / metabolism
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Phenylalanine Hydroxylase / chemistry
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Phenylalanine Hydroxylase / genetics
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Phenylalanine Hydroxylase / isolation & purification
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Phenylalanine Hydroxylase / metabolism*
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Phenylketonurias / genetics
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Recombinant Proteins / chemistry
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Recombinant Proteins / isolation & purification
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Recombinant Proteins / metabolism
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Tyrosine / metabolism
Substances
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Ferrous Compounds
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Recombinant Proteins
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Biopterins
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Tyrosine
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Phenylalanine
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Copper
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Iron
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Phenylalanine Hydroxylase
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sapropterin