Tosyl phenylalanyl chloromethyl ketone (TPCK) is a protease inhibitor

Protease inhibitor (biology)

In biology and biochemistry, protease inhibitors are molecules that inhibit the function of proteases. Many naturally occurring protease inhibitors are proteins....

. Its structural formula

Structural formula

The structural formula of a chemical compound is a graphical representation of the molecular structure, showing how the atoms are arranged. The chemical bonding within the molecule is also shown, either explicitly or implicitly...

 is 1-chloro

Chlorine

Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

-3-tosyl

Tosyl

A tosyl group is CH3C6H4SO2. This group is usually derived from the compound 4-toluenesulfonyl chloride, CH3C6H4SO2Cl, which forms esters and amides of toluenesulfonic or tosylic acid...

amido-4-phenyl-2-butanone

Butanone

Butanone, also known as methyl ethyl ketone or MEK, is an organic compound with the formula CH3CCH2CH3. This colorless liquid ketone has a sharp, sweet odor reminiscent of butterscotch and acetone. It is produced industrially on a large scale, and also occurs in trace amounts in nature...

.

Uses

TPCK is the irreversible inhibitor of chymotrypsin

Chymotrypsin

Chymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin preferentially cleaves peptide amide bonds where the carboxyl side of the amide bond is a tyrosine, tryptophan, or phenylalanine. These amino acids contain an aromatic ring in their sidechain that fits into a...

. Also inhibits some cysteine

Cysteine

Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...

 protease

Protease

A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....

s such as papain

Papain

Papain, also known as papaya proteinase I, is a cysteine protease enzyme present in papaya and mountain papaya .-Papain family:...

, bromelain

Bromelain

Bromelain is a pineapple extract thought to be effective for reducing swelling , especially of the nose and sinuses, after surgery or injury. It may also be used for a variety of other effects that remain scientifically unconfirmed and not authorized by regulatory authorities like the Food and Drug...

 or ficin. It does not inhibit trypsin

Trypsin

Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...

 or zymogens.

TPCK is chosen for the chemical labelling of active histidine in enzyme analysis. The phenylalanine moiety is bound to the enzyme because of specificity for aromatic amino acid residues at the active site (as in chymotrypsin

Chymotrypsin

Chymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin preferentially cleaves peptide amide bonds where the carboxyl side of the amide bond is a tyrosine, tryptophan, or phenylalanine. These amino acids contain an aromatic ring in their sidechain that fits into a...

, in which it binds to the Histidine-57

Sequence of proteases - chymotrypsin A - trypsin - elastase

In the catalytic triad of chymotrypsin, trypsin, and elastase, the three proteases function at three important molecular 'cutting' points. The sites are at amino acid residues of: histidine 57, aspartic acid 102, and serine 195....

residue in the active site).