If measurements are taking by absorption then lysozyme, chymotrypsinogen, trypsinogen, horse heart apomyoglobin, ribonuclease can be used as model compounds because they all are tryptophan-containing proteins

Thank you for your answer K. Shahzad Baig

Regards

Regarding to my question, I forgot to say that we want to perform the tryptophan determinations in pseudocereals. Also to clarify my question I considered necessary to dig more into the methods reported in the literature. Here I further describe the enzymatic method used to determined the concentration of tryptophan, whych is in fact a chemo-enzymatic method.

The first part of the method is the hydrolysis of the proteins and the second part is the reaction. The reaction part is based on the formation of a colored compound resulting from the reaction between tryptophan, acetic acid containing iron ions, and sulfuric acid (Opienska-Blauth et al. 1963, Analytical Biochemistry 6, 69-76). These authors obtained their protein hydrolyzates by the successive action of pepsin and trypsin. Another reference using this method employs papain for protein hydrolysis instead.The method reported in the question by Spies (1967) uses a similar colorimetric determination of the hydrolyzates, but uses Pronase as the proteolytic enzyme. I found that Pronase is a commercial mixture of proteases from Streptomyces griseus which gives an almost complete protein digestion.

With this consideration, it seems that for performing the method described in the literature I only need to use a protease with a very good proteolytic performance. Which common and commercial enzymes can do the work?

In L-tryptophan metabolism, tryptophan synthase is one of the important enzymes that affect the yield of L-tryptophan.Apr 5, 2020

https://www.ncbi.nlm.nih.gov › pmc

Engineering Improves Enzymatic Synthesis of L-Tryptophan ... - NCBI