<prompt> Answer this question truthfullyWhat is the process by which tyrosine is converted to dihydroxyphenylalanine DOPA, and what enzyme is involved in this process along with its cofactor?  <response>: <reason> Tyrosine is an amino acid that can be converted to dihydroxyphenylalanine DOPA through a biochemical pathway that involves the enzyme tyrosine hydroxylase, which requires tetrahydrobiopterin as a cofactor. This conversion is an important step in the synthesis of various neurotransmitters and hormones, including dopamine, norepinephrine, and epinephrine. Tyrosine hydroxylase is a key enzyme in the regulation of these signaling molecules, and its activity can be modulated by various factors, including stress, drugs, and disease states. 