Structure of Trypsin

Trypsin is an enzyme whose function is to degrade dietary protein molecules into their component peptides and amino acids. It is often referred to as proteinase (a proteolytic enzyme). The digestive system, as a whole, acts with the assistance of three primary proteinases that include trypsin, pepsin, and chymotrypsin. All three proteinases work together to break down proteins.

• Molecule

The Facts

• Digestion begins in the stomach and continues into the small intestine, where trypsin is found. The small intestine has a pH level of about 8, meaning that it is slightly alkaline, ideal for maximal enzyme activity. At 5 degrees Celsius, trypsin (as a dry powder) is stable for many years.

Introduction

• Trypsin is produced by the pancreas and it is very similar in structure, in chemical composition, and in mechanism of action to chymotrypsin, the primary pancreatic proteinase. In particular, both enzymes contain residues of histidine (an essential amino acid) and serine an (organic compound), in the enzymes' active sites.

Structure

• Trypsin is formed by the cleavage (or coming together) of inactive precursor trypsinogen (pancreatic enzyme), according to "Enzymes of Molecular Biology" by Michael M. Burrell. It is then activated by a limited proteolytic cleavage at a single peptide bond and the process is catalyzed by numerous enzymes including mold proteases, enterokinase, and trypsin itself. Furthermore, trypsin is active only against the protein molecule peptide bonds which have carboxyl groups donated by the amino acids arginine and lysine.

Specification

• Of all the proteolytic enzymes, trypsin is most restrictive in terms of the number of the chemical bonds that it breaks. In particular, its protease activity is restricted to the positively charged side chains of lysine and arginine. Furthermore, according to Burrell, trypsin also has the ability to hydrolyze ester and amide linkages of the synthetic derivatives of lysine and arginine.

Considerations

• In the 1970's, trypsin was isolated from a variety of sources, including moose, whale, elephant seal, pigs, humans, and dogfish. It has the ability to exhibit both esterase (an enzyme that splits esters into an acid and an acohol) and amidase (an enzyme that catalyzes chemical reactions) activities. Trypsin is inhibited by a variety of organophosphorous compounds that include natural trypsin inhibitor (found in the pancreas) and diisopropyl fluorophosphate. Other inhibitors include lima beans, egg whites, and soybeans. Silver ion is also a trypsin inhibitor. On the other hand, trypsin activation is stimulated through the use of lanthanide ions.