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A protein kinase is a kinase which selectively modifies other proteins by covalently adding phosphates to them (phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules. Phosphorylation usually results in a functional change of the target protein (substrate) by changing enzyme activity, cellular location, or association with other proteins. The human genome contains about 500 protein kinase genes and they constitute about 2% of all human genes. There are two main types of protein kinase. The great majority are serine/threonine kinases, which phosphorylate the hydroxyl groups of serines and threonines in their targets. Most of the others are tyrosine kinases, although additional types exist. Protein kinases are also found in bacteria and plants. Up to 30% of all human proteins may be modified by kinase activity, and kinases are known to regulate the majority of cellular pathways, especially those involved in signal transduction.
A metalloproteinase, or metalloprotease, is any protease enzyme whose catalytic mechanism involves a metal. An example is ADAM12 which plays a significant role in the fusion of muscle cells during embryo development, in a process known as myogenesis.
DD-transpeptidase is a bacterial enzyme that catalyzes the transfer of the R-L-αα-D-alanyl moiety of R-L-αα-D-alanyl-D-alanine carbonyl donors to the γ-OH of their active-site serine and from this to a final acceptor. It is involved in bacterial cell wall biosynthesis, namely, the transpeptidation that crosslinks the peptide side chains of peptidoglycan strands.
Papain, also known as papaya proteinase I, is a cysteine protease enzyme present in papaya and mountain papaya. It is the namesake member of the papain-like protease family.
A catalytic triad is a set of three coordinated amino acids that can be found in the active site of some enzymes. Catalytic triads are most commonly found in hydrolase and transferase enzymes. An acid-base-nucleophile triad is a common motif for generating a nucleophilic residue for covalent catalysis. The residues form a charge-relay network to polarise and activate the nucleophile, which attacks the substrate, forming a covalent intermediate which is then hydrolysed to release the product and regenerate free enzyme. The nucleophile is most commonly a serine or cysteine amino acid, but occasionally threonine or even selenocysteine. The 3D structure of the enzyme brings together the triad residues in a precise orientation, even though they may be far apart in the sequence.
Endopeptidase Clp (EC 3.4.21.92, endopeptidase Ti, caseinolytic protease, protease Ti, ATP-dependent Clp protease, ClpP, Clp protease). This enzyme catalyses the following chemical reaction
Tissue kallikrein is an enzyme. This enzyme catalyses the following chemical reaction
Subtilisin is a protease initially obtained from Bacillus subtilis.
Aspartic proteases 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. Nearly all known aspartyl proteases are inhibited by pepstatin.
Thermolysin is a thermostable neutral metalloproteinase enzyme produced by the Gram-positive bacteria Bacillus thermoproteolyticus. It requires one zinc ion for enzyme activity and four calcium ions for structural stability. Thermolysin specifically catalyzes the hydrolysis of peptide bonds containing hydrophobic amino acids. However thermolysin is also widely used for peptide bond formation through the reverse reaction of hydrolysis. Thermolysin is the most stable member of a family of metalloproteinases produced by various Bacillus species. These enzymes are also termed 'neutral' proteinases or thermolysin -like proteinases (TLPs).
Carboxypeptidase B is a carboxypeptidase that preferentially acts upon basic amino acids, such as arginine and lysine. This serum enzyme is also responsible for rapidly metabolizing the C5a protein into C5a des-Arg, with one less amino acid.
The enzyme Acid-Induced Arginine Decarboxylase (AdiA), also commonly referred to as arginine decarboxylase, catalyzes the conversion of L-arginine into agmatine and carbon dioxide. The process consumes a proton in the decarboxylation and employs a pyridoxal-5'-phosphate (PLP) cofactor, similar to other enzymes involved in amino acid metabolism, such as ornithine decarboxylase and glutamine decarboxylase. It is found in bacteria and virus, though most research has so far focused on forms of the enzyme in bacteria. During the AdiA catalyzed decarboxylation of arginine, the necessary proton is consumed from the cell cytoplasm which helps to prevent the over-accumulation of protons inside the cell and serves to increase the intracellular pH. Arginine decarboxylase is part of an enzymatic system in Escherichia coli, Salmonella Typhimurium, and methane-producing bacteria Methanococcus jannaschii that makes these organisms acid resistant and allows them to survive under highly acidic medium.
Kexin is a prohormone-processing protease, specifically a yeast serine peptidase, found in the budding yeast. It catalyzes the cleavage of -Lys-Arg- and -Arg-Arg- bonds to process yeast alpha-factor pheromone and killer toxin precursors. The human homolog is PCSK4. It is a family of subtilisin-like peptidases. Even though there are a few prokaryote kexin-like peptidases, all kexins are eukaryotes. The enzyme is encoded by the yeast gene KEX2, and usually referred to in the scientific community as Kex2p. It shares structural similarities with the bacterial protease subtilisin. The first mammalian homologue of this protein to be identified was furin. In the mammal, kexin-like peptidases function in creating and regulating many differing proproteins.
In enzymology, a [acyl-carrier-protein] S-malonyltransferase is an enzyme that catalyzes the chemical reaction
Subtilases are a family of subtilisin-like serine proteases. They appear to have independently and convergently evolved an Asp/Ser/His catalytic triad, like in the trypsin serine proteases. The structure of proteins in this family shows that they have an alpha/beta fold containing a 7-stranded parallel beta sheet.
Signal peptidases are enzymes that convert secretory and some membrane proteins to their mature or pro forms by cleaving their signal peptides from their N-termini.
Endopeptidase So is an enzyme. This enzyme catalyses the following chemical reaction
Signal peptidase II is an enzyme.
Mitochondrial processing peptidase is an enzyme complex found in mitochondria which cleaves signal sequences from mitochondrial proteins. In humans this complex is composed of two subunits encoded by the genes PMPCA, and PMPCB. The enzyme is also known as. This enzyme catalyses the following chemical reaction
Oligopeptidase A is an enzyme. This enzyme catalyses the following chemical reaction
References
- ↑ Black MT (August 1993). "Evidence that the catalytic activity of prokaryote leader peptidase depends upon the operation of a serine-lysine catalytic dyad". Journal of Bacteriology. 175 (16): 4957–61. doi:10.1128/jb.175.16.4957-4961.1993. PMC 204959 . PMID 8394311.
- ↑ Nunnari J, Fox TD, Walter P (December 1993). "A mitochondrial protease with two catalytic subunits of nonoverlapping specificities". Science. 262 (5142): 1997–2004. doi:10.1126/science.8266095. PMID 8266095.
- ↑ Tschantz WR, Sung M, Delgado-Partin VM, Dalbey RE (December 1993). "A serine and a lysine residue implicated in the catalytic mechanism of the Escherichia coli leader peptidase". The Journal of Biological Chemistry. 268 (36): 27349–54. PMID 8262975.
- ↑ Lively MO, Newsome AL, Nusier M (1994). Eukaryote microsomal signal peptidases. Methods in Enzymology. Vol. 244. pp. 301–14. doi:10.1016/0076-6879(94)44024-7. PMID 7845216.
- ↑ Tschantz WR, Dalbey RE (1994). Bacterial leader peptidase 1. Methods in Enzymology. Vol. 244. pp. 285–301. doi:10.1016/0076-6879(94)44023-9. PMID 7845215.
- ↑ Chaal BK, Mould RM, Barbrook AC, Gray JC, Howe CJ (January 1998). "Characterization of a cDNA encoding the thylakoidal processing peptidase from Arabidopsis thaliana. Implications for the origin and catalytic mechanism of the enzyme". The Journal of Biological Chemistry. 273 (2): 689–92. doi: 10.1074/jbc.273.2.689 . PMID 9422718.
- ↑ Inoue K, Baldwin AJ, Shipman RL, Matsui K, Theg SM, Ohme-Takagi M (November 2005). "Complete maturation of the plastid protein translocation channel requires a type I signal peptidase" (PDF). The Journal of Cell Biology. 171 (3): 425–30. doi: 10.1083/jcb.200506171 . PMC 2171254 . PMID 16275749.
