Allosteric regulation of phenylalanine hydroxylase

The liver enzyme phenylalanine hydroxylase is responsible for conversion of excess phenylalanine in the diet to tyrosine. Phenylalanine hydroxylase is activated by phenylalanine; this activation is inhibited by the physiological reducing substrate tetrahydrobiopterin. Phosphorylation of Ser16 lowers the concentration of phenylalanine for activation. This review discusses the present understanding of the molecular details of the allosteric regulation of the enzyme.

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► Phenylalanine hydroxylase is activated by phenylalanine.
► Phenylalanine activation is greatest with tetrahydrobiopterin as substrate.
► Ser16 phosphorylation lowers the phenylalanine concentration needed for activation.
► Activation is accompanied by altered interactions between domains.