Substrate specificity and other properties of DOPA decarboxylase from guinea pig kidneys

DOPA decarboxylase (aromatic-l-amino-acid carboxy-lyase, EC 4.1.1.28) from guinea pig kidneys has been purified to a specific activity of 9370 or 330-fold. Efficient purification was possible by employing apolar interaction chromatography. The purified enzyme gives a single component on polyacrylamide gel electrophoresis and the absorption spectrum of the enzyme reveals two forms of binding of pyridoxal 5-phosphate. The pure enzyme decarboxylates l-DOPA, 5-hydroxytryptophan, o-tyrosine and m-tyrosine but it is inactive towards phenylalanine, tyrosine, tryptophan, histidine and 3-methoxy-phenylalanine. The enzyme behaves as an undissociated enzyme but only towards 5-hydroxytryptophan. It behaves as an enzyme from which the coenzyme is partially dissociated when it attacks l-DOPA, o-tyrosine and m-tyrosine.