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Ribbon diagram of a protease (TEV protease) complexed with its peptide substrate in black with catalytic residues in red.(. A protease (also called a peptidase, proteinase, or proteolytic enzyme) [1] is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. [2]
Proteases are a class of enzymes that regulate much of what happens in the human body, both inside the cell and out, by cleaving peptide bonds in proteins.Through this activity, they govern the four essential cell functions: differentiation, motility, division and cell death — and activate important extracellular episodes, such as the biochemical cascade effect in blood clotting.
The active site consists of amino acid residues that form temporary bonds with the substrate, the binding site, and residues that catalyse a reaction of that substrate, the catalytic site. Although the active site occupies only ~10–20% of the volume of an enzyme, [ 1 ] : 19 it is the most important part as it directly catalyzes the chemical ...
Proteases in particular are synthesized in the inactive form so that they may be safely stored in cells, and ready for release in sufficient quantity when required. This is to ensure that the protease is activated only in the correct location or context, as inappropriate activation of these proteases can be very destructive for an organism.
Aspartic proteases (also "aspartyl proteases", "aspartic endopeptidases") are a catalytic type of protease enzymes that use an activated water molecule bound to one or more aspartate residues for catalysis of their peptide substrates. In general, they have two highly conserved aspartates in the active site and are optimally active at acidic pH.
The structure of chymotrypsin was solved by X-ray crystallography in the 1960s, showing the orientation of the catalytic triad in the active site. [8] Other proteases were sequenced and aligned to reveal a family of related proteases, [9] [10] [11] now called the S1 family.
The molecule ritonavir, marketed as Norvir, was developed as a protease inhibitor and used to target HIV infection. However, it has been shown to inhibit proteasomes as well as free proteases; to be specific, the chymotrypsin-like activity of the proteasome is inhibited by ritonavir, while the trypsin-like activity is somewhat enhanced. [113]
There are four groups of intramembrane proteases, distinguished by their catalytic mechanism: [5]. Metalloproteases: Site-2 protease (S2P) and S2P-like proteases [9]; Aspartyl proteases: this group includes presenilin, the active subunit of gamma secretase [10] [11] and signal peptide peptidases (SPPs) and SPP-like proteases, which are distantly related to presenilin but have opposite membrane ...