FIGURE 6.
Functional consequence of GTPCH-TH interaction on TH specific activity in the presence of excess cofactor. Recombinant phosphorylated His6-TH was assayed for activity after being mixed with 500 μm BH4 and varying molar concentrations of recombinant phosphorylated His6-GTPCH isoform C. TH enzyme activity was unaffected by the presence of GTPCH in any molar ratio. Reactions containing only GTPCH were used as negative controls. The specific activity of TH is expressed as nmol of its product, l-DOPA, generated per min per mg of recombinant TH in the reaction mix. Values are the means ± S.E. of four determinations.