The biosynthesis of the amino acid tyrosine occurs through a series of enzymatic reactions. The primary pathway for tyrosine biosynthesis is derived from the essential amino acid phenylalanine. Here is the order of enzymatic reactions involved in the biosynthesis of tyrosine:1. Phenylalanine hydroxylase PAH reaction:The first step in the biosynthesis of tyrosine is the hydroxylation of phenylalanine to form tyrosine. This reaction is catalyzed by the enzyme phenylalanine hydroxylase PAH . PAH is a non-heme iron-containing enzyme that uses molecular oxygen and the cofactor tetrahydrobiopterin BH4 to hydroxylate the phenylalanine at the para-position of the phenyl ring. The reaction mechanism involves the formation of a high-valent iron-oxo intermediate, which abstracts a hydrogen atom from the phenylalanine substrate. This leads to the formation of a phenyl radical, which then reacts with the hydroxyl group to form tyrosine.2. Prephenate dehydrogenase PDH reaction:In some microorganisms, tyrosine can also be synthesized from chorismate through the prephenate pathway. The first enzyme in this pathway is prephenate dehydratase, which converts chorismate to prephenate. The next enzyme, prephenate dehydrogenase PDH , catalyzes the oxidative decarboxylation of prephenate to form 4-hydroxyphenylpyruvate. PDH is an NAD+-dependent enzyme, and the reaction proceeds through the formation of a Schiff base intermediate between the enzyme and the substrate. The decarboxylation step is followed by the reduction of the imine intermediate to form 4-hydroxyphenylpyruvate.3. 4-Hydroxyphenylpyruvate dioxygenase HPPD reaction:The final step in the biosynthesis of tyrosine is the conversion of 4-hydroxyphenylpyruvate to tyrosine. This reaction is catalyzed by the enzyme 4-hydroxyphenylpyruvate dioxygenase HPPD . HPPD is a non-heme iron-containing enzyme that uses molecular oxygen to insert an oxygen atom between the keto group and the phenyl ring of 4-hydroxyphenylpyruvate. The reaction proceeds through the formation of a high-valent iron-oxo intermediate, which attacks the keto group of the substrate to form a cyclic intermediate. This intermediate then undergoes a rearrangement and hydrolysis to release tyrosine and carbon dioxide.In summary, the order of enzymatic reactions involved in the biosynthesis of tyrosine is as follows:1. Phenylalanine hydroxylase PAH reaction: Phenylalanine Tyrosine2. Prephenate dehydrogenase PDH reaction in some microorganisms : Chorismate Prephenate 4-Hydroxyphenylpyruvate3. 4-Hydroxyphenylpyruvate dioxygenase HPPD reaction: 4-Hydroxyphenylpyruvate Tyrosine