Tyrosine

Tyrosine is an aromatic amino acid, which can absorb light. It consists of phenylalanine formed by the reaction catalyzed by phenylalanine hydroxylase. Phenylalanine is essential amino acid, but tyrosine is not, provided that the diet contains sufficient amounts of phenylalanine. The reaction is not reversible, whereas tyrosine can not replace the requirement for phenylalanine. Tyrosine is to save the action, because if the tyrosine is supplied then need to phenylalanine in the body decreases. The two amino acids are ketogenic and glycogenic same. Both have a huge metabolic role of the body and are metabolized through normal channels. The catabolism of tyrosine results in the formation of aceto-acetic acid, phenol, tyramine, epinephrine (adrenaline), non-epinephrine (adrenaline, nor), thyroid hormones, and melanin in distinct reactions.

Tyrosine is essential for the synthesis of proteins and serves as a precursor for thyroxin, melanin, and catecholamines.

Tyrosine, an amino acid, found in chicken and tuna also stimulates brain chemicals that improve the motivation and reaction time. Heredity defective metabolic abnormalities lead to tyrosine tyrosinosis, alcaptonuria (occhronosis), and albinism, which are described below.

The excess of tyrosine, when levels of serum tyrosine levels are 6-12 mg / dl than those of methionine, a condition called tyrosinosis, affecting enzyme activities and various transport systems. In acute tyrosinosis, infants with diarrhea, vomiting with a cabbage, as the smell and fail to thrive. Without treatment, death from liver failure occurs in 6-8 months. In tyrosinosis chronic symptoms are similar, but milder, and death occurs by 10 years of age. Treatment includes a diet low in phenylalanine and tyrosine also sometimes low, even in methionine.

The other metabolic defect is tyrosinosis. Type II, where tyrosine in serum increased to 4-5 mg / dl, is hepatic with eyes and skin lesions, and some mental retardation. It is the only amino acid whose urinary concentration is high while the renal clearance and reabsorption of the fall of the tyrosine within normal limits.

Another disorder, tyrosinosis neonatal blood levels in which the tyrosine and phenylalanine are high, the urinary level of tyrosine is raised. Treatment consists of a diet low in protein.

Melanins are polymers of tyrosine catabolites, catalyzed by tyrosine hydroxylase. Albino with tyrosine hydroxylase: the missing negative all the visual pigments and hair follicles are unable to convert tyrosine into pigment added, as have positive visual pigments and hair follicles convert tyrosine to black eumelanin in vitro.

Tyrosine forms of adrenaline and adrenaline, or on obtaining converted into cells of neural origin by enzymes in adrenal medulla. The rate-limiting enzyme in the biosynthetic pathway of catecholamines is tyrosine hydroxylase. Tyrosine is also a precursor of thyroid hormones. free tyrosine can be iodinated by organification reaction. The ascorbic acid (vitamin C) is necessary for degradation of tyrosine, and also in the synthesis of adrenaline from tyrosine.

Sources of tyrosine: It is available mainly in ragi, parboiled rice, cowpea, pea, soybean, pumpkin leaves, spinach, Colocasia, yams, lady fingers, brinjal, grount nuts, sesame seeds, figs, strawberries, curd, milk.

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