<prompt> Answer this question truthfullyWhat is the conversion process and what are the required enzyme and cofactor involved in the biosynthesis of tyrosine from phenylalanine?  <response>: <reason> The conversion of phenylalanine to tyrosine is carried out by the enzyme phenylalanine hydroxylase, which requires the presence of tetrahydrobiopterin as a cofactor. This process is an essential step in the biosynthesis of tyrosine, which is an amino acid that plays a crucial role in protein synthesis and other metabolic processes in the body. 