Phenylketonuria-A condition caused by a genetic error of the body's metabolism, characterized by the absence of phenylalanine hydroxylase (an enzyme that converts phenylalanine into tyrosine).
The hairbulb pigmentation test is used to identify carriers by incubating a piece of the person's hair in a solution of tyrosine, a substance in food which the body uses to make melanin.
It measures the rate at which hair converts the amino acid tyrosine into another chemical (3,4-dihydroxyphenylalanine, or DOPA), which is then made into pigment.
Typical diets prescribed for PKU patients provide very small amounts of phenylalanine and higher quantities of other amino acids, including tyrosine.
Another, more accurate test procedure for PKU measures the ratio (comparison) of the amount of phenylalanine to the amount of tyrosine in the blood.
Thus, some health professionals recommend adding time-released tyrosine that can provide a more constant supply of this amino acid to the body.
This abnormality may explain why many PKU patients who receive sufficient dietary tyrosine still experience some form of learning disability.
In some types of albinism, a genetic defect in tyrosinase means that the amino acid tyrosine cannot be converted by tyrosinase into melanin.
Each of the products are infused with the patented Cellex-C complex, a powerful combination of L-ascorbic acid, tyrosine and zinc.
Nh]]�CH2�CH2�CH2, hydroxyproline, phenyl alanine or phenyl-a-aminopropionic acid, C 6 H 5 � CH 2 � CH(NH 2) � Cooh, tyrosine or p-hydroxyphenyl-aaminopropionic acid, phenyl ethylamine, p-hydroxyphenyl ethylamine, tryptophane or indol aminopropionic acid, A.
