Phenylalanine hydroxylase (PHA) performs an enzymatic function during the conversion of phenylalanine, to tyrosine. Existing naturally in several types of foods, for instance, breast milk, PKU is an essential α-amino acid and one of the plethora of amino acids used in the formation of proteins. Phenylalanine exists in three forms; L-phenylalanine, D-phenylalanine (mirror image of L-phenylalanine), and DL-phenylalanine which is a typic combination of D and L-phenylalanine, and unlike D and L- phenylalanine, is not found in foods. On the other hand, tyrosine, apart from being a derivative of phenylalanine, is a non-essential amino acid that forms part of the list of amino acids utile during the constitution of proteins. Ordinarily, lack of PAH leads to the accumulation of phenylalanine (the phenylalanine is not converted to tyrosine) leading to the development of a disease called Phenylketonuria (PKU).
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