RECOMBINANT RABBIT TRYPTOPHAN-HYDROXYLASE IS A SUBSTRATE FOR CAMP-DEPENDENT PROTEIN-KINASE

A full-length cDNA clone for rabbit tryptophan hydroxylase (TPH) was m odified and subcloned into a bacterial expression vector. Expression o f this gene in the protease-deficient strain of bacteria, BL21[DE3], p roduced TPH immunoreactive protein which exhibited enzyme activity. Tr eatment of the recombinant enzyme (in bacterial extracts) with the pur ified catalytic subunit of the cAMP-dependent protein kinase and [y-P- 32]-ATP resulted in specific phosphorylation of TPH. This expression s ystem provides a means of generating and purifying large amounts of th is important enzyme. Moreover, these experiments establish that TPH wi ll serve as an in vitro substrate for cAMP-dependent protein kinase.