JBC, Vol. 250, Issue 17, 6672-6678, Sep, 1975
Phenylalanine hydroxylase from Pseudomonas sp. (ATCC 11299a). Purification, molecular weight, and influence of tyrosine metabolites on activation and hydroxylation
C. H. Letendre, G. Dickens and G. Guroff
Phenylalanine hydroxylase from Pseudomonas sp. (ATCC 11299a) has been
purified 25- to 30-fold by a procedure which has been modified from that
previously described for this organism (Guroff, G., and Ito, T. (1965) J.
Biol. Chem. 240, 1175-1184; Guroff, G., and Rhoads, C. A. (1967) J. Biol.
Chem. 242, 3641-3645). Further purification yielded a preparation which was
judged to be about 80% pure by sodium dodecyl sulfate-containing and
standard analytical polyacrylamide gels, but the activity in this
preparation has proved to be very labile. The enzyme appears to be a single
protein chain of between 25,000 to 27,000 molecular weight. Phenylalanine,
tyrosine, and tryptophan inhibit the activation of the enzyme by iron in a
competitive fashion. The tyrosine metabolites, p-hydroxyphenylpyruvic and
homogentisic acids exhibit a biphasic effect on activation, stimulating at
low iron, and inhibiting at higher iron concentrations. The hydroxylation
itself is inhibited by tyrosine and related compounds such as
L-3,4-dihydroxyphenylalanine and dopamine. p-Hydroxyphenylpyruvic acid is a
competitive inhibitor with respect to both substrate and cofactor. The data
indicate a variety of means by which the bacterium can regulate
phenylalanine hydroxylation.
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