PAH

Tyrosine hydrolase (TYH) is the enzyme which converts tyrosine to dihydroxyphenylalanine (L-dopa), a precursor of the catecholamine neurotransmitters dopamine, noradrenaline and adrenaline. Tryptophan hydrolase (TRH) is the enzyme that converts 5-hydroxytryptophan to serotonin. TRH can be used as a marker for serotonin as it converts 5-hydroxy-tryptophan to serotonin. Serotonin is rapidly metabolized and is unable to be detected by anti-serotonin antibodies in post mortem tissue. In human tissue that has been formalin-fixed, due to a change in the antigenic determinant of TYH, this product will bind only TRH. The antibody can therefore be used to specifically identify serotonergic neurons in fixed human tissues. Phenylalanine hydrolase (PAH) can be detected in hepatic tissue sections.