Serine proteases
| Serine proteases | ||
|---|---|---|
| Enzyme classification | ||
| EC, category | 3.4.21. , Peptidase | |
| Response type | Proteolysis | |
Serine proteases are a subfamily of peptidases (i.e. enzymes that split proteins and peptides ).
The division into this group relates to the active center of the peptidases. Like all enzymes, serine proteases also have a very specific structure in the active center, here the catalytic triad . The amino acid serine is found in the serine proteases .
Serine proteases include the digestive enzymes trypsin , chymotrypsin , elastase as well as plasmin and thrombin , both of which play a crucial role in blood coagulation , and finally also the granzymes used by cytotoxic T cells to kill infected or degenerated cells in the body .
Catalyzed reaction
inhibition
An inhibition of serine proteases takes place in the body, for example, by certain proteins, the serpins , in order to switch off the serine protease after work is done. A lack of these inhibitors leads to thrombosis (example antithrombin ) or pulmonary emphysema (example antitrypsin ). In such cases, man-made inhibitors such as AEBSF and phenylmethylsulfonyl fluoride can be given .
The serine proteases are subject to highly differentiated control through a network of interacting cascades of inhibiting substances. Two forms can be distinguished.
Nonspecific inhibition
One way of inhibiting proteases is to enclose them in a cage. The alpha-2 macroglobulin surrounds activated proteases like a mousetrap. Serine proteases such as prekallikrein and thrombin are inactivated.
Specific inhibition
Another form of inhibition of serine proteases is a highly specific one by Serpine, a class of serine protease inhibitors. Many of the enzymes of the coagulation system are such serine proteases and serine protease inhibitors.
Classification according to UniProt / MEROPS
The UniProt Consortium regularly publishes a list of peptidases that categorize these enzymes according to their evolutionary origin. The data in the list are provided with high-quality information and can be called up in the MEROPS database. Closely related molecules are grouped together in families whose names consist of a letter ('S' for serine proteases) and a number. Families, in turn, belong to clans whose families are related. Clan identifiers have a letter instead of numbers.
There are 45 serine protease families in 13 clans (as of 2008), with clan PA (S) with 12 families being of outstanding importance.
| clan | description | Exemplary enzyme | UniProt | Familys |
|---|---|---|---|---|
| PA (S) | Endopeptidases with cat. Center His-Asp-Ser | Chymotrypsin A ( Bos taurus ) | P00766 | S1 S3 S6 S7 S29 S30 S31 S32 S39 S46 S55 S64 |
| PB (S) | Autolytic peptidases. No peptidase activity after autolysis. Ser at the N-terminus. | Penicillin G acylase ( E. coli ) | P06875 | S45 |
| PC (S) | Peptidases with cat. Center Ser-His-Glu | Dipeptidase E ( Salmonella typhimurium ) | Q1R3S5 | S51 |
| SB | Subtilase family, endo- and exopeptidases | Subtilisin Carlsberg ( Bacillus licheniformis ) | P00780 | S8 S53 |
| SC | Endo- and exopeptidases with cat. Center Ser-Asp-His | Serine carboxypeptidase D ( Triticum aestivum ) | P08819 | S9 S10 S15 S28 S33 S37 |
| SE | Spec. Peptidases in the metabolism of bacterial cell walls | D-Ala-D-Ala-Carboxypeptidase B ( Streptomyces sp ) | P15555 | S11 S12 S13 |
| SF | Endopeptidases with cat. Center Ser-His (Lys) | UmuD protein ( E. coli ) | P0AG11 | S24 S26 |
| SH | DNA virus endopeptidases with cat. Center His-Ser-His | Assemblin (HHV-5) | P16753 | S21 |
| SJ | Endopeptidases with cat. Center Ser-Lys | Lon A peptidase ( E. coli ) | P0A9M0 | S16 S50 S69 |
| SK | Endopeptidases with cat. Center Ser-His-Asp | Peptidase Clp type 1 ( E. coli ) | Q1RF98 | S14 S41 S49 |
| SP | Autopeptidases with cat. Center His-X-Ser | Nucleoporin 145 ( Homo sapiens ) | P52948 | S59 |
| SQ | Aminopeptidase DmpA ( Ochrobactrum anthropi ) | S58 | ||
| SR | Endopeptidases with cat. Center Lys-Ser | Lactoferrin ( Homo sapiens ) | P02788 | S60 |
| SS | Amidopeptidases with cat. Center Ser-Glu-His | S66 | ||
| ST | Transmembrane peptidases with transmembrane domains as substrates | S58 | ||
| S- | without assignment | S48 S62 S63 S68 S71 S72 |
Important serine proteases
- the digestive enzymes trypsin , chymotrypsin , elastase (S1)
- prostate-specific antigen and tryptases (S1)
- the blood coagulation factors plasmin , thrombin , Christmas factor , Hageman factor , factor VII-activating protease , kallikrein (S1) and Stuart Prower factor (S2)
- MBTPS1 and Proteinase K (S8)
- Dipeptidyl peptidase 4 (S9)
- the granzyme responsible for the apoptosis of the body's own and foreign cells