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 .
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 .