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  • Title: Expression and characterization of the catalytic domain of human phenylalanine hydroxylase.
    Author: Daubner SC, Hillas PJ, Fitzpatrick PF.
    Journal: Arch Biochem Biophys; 1997 Dec 15; 348(2):295-302. PubMed ID: 9434741.
    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.
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