Tryptophan decarboxylase from Catharanthus roseus is a pyridoxoquinoprotein

Tryptophan decarboxylase (EC 4.1.1.28) from Catharanthus roseus was purified to homogeneity. The native enzyme has an M r of about 96000 as estimated from native PAGE. After SDS‐PAGE, three protein bands were visible corresponding with M r 49000, 33000 and 17000. The N‐termini of the 49 kDa protein and the 33 kDa protein were identical. Antibodies against the 49 kDA protein also reacted strongly with the two smaller proteins. It is concluded that the native enzyme consists of two subunits of M r 49000. Tryptophan decarboxylase appears to be a pyridoxo‐quinoprotein, since two molecules of pyridoxal phosphate and two molecules of covalently‐bound pyrroloquinoline quinone were found per enzyme molecule.