Naturally Occurring Trypsin Inhibitors

Naturally Occurring Trypsin Inhibitors M. Laskowski and M. Laskowski, Jr. 

This enzyme [EC 3.4.21.10] catalyzes the hydrolysis of Arg-Xaa and Lys-Xaa peptide bonds. The enzyme belongs to the peptidase family SI and is inhibited by naturally occurring trypsin inhibitors. 

M. Laskowski and M.Laskowski Jr., Naturally Occurring Trypsin Inhibitors, Adv. Protein Chem. 9, 203-242 (1954). 

Of special interest is the reaction of an acyl enzyme with active-site-directed inhibitors in comparison with the free enzyme. Therefore, we studied the hydrolysis of the substrate Bz-Arg-pNA by trypsin and benzoyl-trypsin in the presence of the naturally occurring inhibitor aptotinin [21]. The substrate is cleft... 

Skills in separation of grain components and their analysis are needed to address these problems. Some examples of naturally occurring antinutritional compounds are phytates (already mentioned), phenols, tannins, and trypsin- and a-amylase inhibitors. Phenols and tannins bind with and precipitate proteins in food systems, thus decreasing digestibility. Minimizahon of these compounds in cereals is an objective. 

Trypsin is inhibited by DFP in the same manner as chymotrypsin one P per mole (M.W., 24,000). It is also inhibited by naturally occurring proteins, several of which have been crystallized as trypsin inhibitors. These inhibitors act by forming stoichiometric compounds with trypsin irreversibly. 

The use of X-ray techniques to elucidate the three-dimensional structure of enzymes shows that many of them possess a characteristic concave cleft at the active site. Concavities of this type have been observed, for example, in the case of lysozyme [8, 9] trypsin [10], yeast hexokinase [11], liver alcohol dehydrogenase [12] and citrate synthase [13]. It is thus reasonable to assume that the interaction between an enzyme and its substrate, inhibitor or cofactor usually occurs not in bulk water but rather in a shielded proteic cleft whose specific microenvironment is induced by the amino acid residues forming the cleft. Hydrophobicity, electrostatics, solvation and a relatively low dielectric constant prevailing within the cleft no doubt play a decisive role in determining the nature and rate of the reaction catalyzed by the enzyme. 

---