Role of some structural features of subtrates on trypsin activity

Tryptic hydrolysis of 27 different amides of arginine was studied in an attempt to learn more about the specificity requirements of trypsin. Chain length is important for tryptic action, the optimal length being one which contains four amides (pentalysine) or three amides and one urethane (carbobenzoxy-triarginyl naphthyl amide). The electronic characteristics of the groups blocking the α-amino group of arginine appear to play a role in that the more negatively charged groups are hydrolyzed more readily by trypsin. The properties of the amine attached to the enzyme-sensitive bond also have an influence on tryptic action. Aromatic amides are much more susceptible than simple amides in dipeptide and tripeptide substrates. The three most active substrates, N^α-carbobenzoxydiglycyl-l-arginyl-2-naphthylamine, β-carboxyproprionyl-l-diarginyl-2-naphthylamide, and N^α-carbobenzoxy-l-triarginyl-2-naphthylamide, were found to be split more readily than N^α-benzoyl-l-arginine-2-naphthylamide (BANA) by factors of 220, 147, and 113, respectively. As little as 5 μg of added trypsin per milliliter of serum can be identified in serum. A smaller amount could not be measured in spite of a series of attempts to separate trypsin from the anti-trypsin present in serum.