Tryptophan Hydroxylase in Nucleated Thrombocytes of the Domestic Fowl.

Using the labeled CO₂ trapping method, tryptophan hydroxylase activity was detected in the nucleated thrombocytes of the domestic fowl, but not in the mammalian platelets. This enzyme activity was around a 5-hydroxytryptophan production of 60 pmol×mg protein^-1××h^-1. Certain properties such as optimal pH (7.0), K_m value (12 μM), requirement for cofactor (2-amino-4-hydroxy-6,7-dimethyl-5,6,7,8-tetrahydroptetidine) and inhibition by p-chlorophenylalanine indicated a close resemblance to tryptophan hydroxylase from brain tissue. Solubilization of this enzyme was to some extent successful by digitonin treatment of the cells. [ABSTRACT FROM AUTHOR]