Description_x000D_ Application_x000D_ Apotryptophanase is used for the quantitative determination of pyridoxal-phosphate. Apotryptophanase, from Sigma, has been used to study pregnancy-associated PLP deficiency and vitamin B-6 deficiency ._x000D_ Packaging_x000D_ 25 mg in poly bottle_x000D_ Biochem/physiol Actions_x000D_ Apotryptophanase hydrolizes tryptophan and is capable of catalyzing α,β-elimination reactions with a number of substituted amino acids, including S-methyl-, S-ethyl- and S-benzyl- L-cysteine. DTNB inactivates tryptophanase ._x000D_ Unit Definition_x000D_ One unit releases one μg of indole from L-tryptophan in 10 min at pH 8.3 at 37 °C in the presence of 0.04 mM pyridoxal-5′--phosphate.