Tryptophan 5‐hydroxylase

Abstract

Tryptophan 5-hydroxylase (EC 1.14.16.4; L-tryptophan tetrahydropteridine: oxygen oxidoreductase) was purified to electrophoretic homogeneity from whole brain supernatant using the following steps: pteridine-argarose affinity chromatography, hydrophobic and finally hydroxyapatite chromatography. Exogenous catalase was necessary throughout most of the purification procedure in order to protect the enzyme against inactivation. The iron chelator desferrioxamine at a concentration of 10 microM or higher brought about an irreversible loss of enzyme activity of a partially purified preparation containing an excess of catalase, whereas this same chelator at a lower concentration afforded considerable protection of the enzyme's activity during the final purification stage despite the quasi-total absence of catalase and the presence of an excess of ferrous iron. Antiserum raised in the rabbit to purified tryptophan 5-hydroxylase appears to be monospecific for the enzyme after immunoadsorption of anti-catalase antibodies which were present due to the trace of catalase which remained in the final enzyme preparation.