Pathway: tyrosine biosynthesis IV

In humans, |FRAME: PHE| is an indispensable dietary amino acid, which may either be used for protein synthesis or converted to the amino acid |FRAME: TYR|, the precursor for catecholamine and thyroid hormone synthesis. |FRAME: TYR| is not considered an indispensable component of diet, despite being an essential component of body proteins, because it can be synthesized from |FRAME: PHE| |CITS:[4265522][1093910]|. |FRAME: CPLX-7067| (EC 1.14.16.1) is responsible for the irreversible oxidation of the essential amino acid |FRAME: PHE| to |FRAME: TYR|. The enzyme is found mostly in the liver |CITS: [4004813]| and in the kidney |CITS: [10655515]|, and its subcellular location is the cytoplasm. The enzyme, whose active form is tetrameric, requires the binding of L-phenylalanine to the regulatory domain in order to promote phosphorylation of Ser16, followed by a conformational change, which allows the formation of active tetramers from inactive precursor dimers. Once the active tetrameric form of the enzyme has been produced, |FRAME: PHE| and the cofactor |FRAME: TETRA-H-BIOPTERIN| can bind to the active site domain initiating catalysis. In addition, |FRAME: CPLX-7067| is tightly coupled to |FRAME: CPLX-7068| (EC 4.2.1.96), the key enzyme that is responsible for the recycling of the cofactor |FRAME: TETRA-H-BIOPTERIN|. It has been shown that |FRAME: CPLX-7068| increases the rate of |FRAME: CPLX-7067| 7-fold, and converts the product |FRAME: CPD-5881| to |FRAME: BIOPTERIN| by dehydration, which is further reduced to |FRAME: TETRA-H-BIOPTERIN| in the presence of NADH by |FRAME: CPLX-7069| (EC 1.6.99.7).