Aminopeptidases are enzymes that catalyze the cleavage of amino acids from the beginning, or N-terminus, of proteins or peptides. They are found in many organisms, being found in many cellular organelles, in the internal cellular fluid, and as components of membranes. Aminopeptidases are used in some essential cellular functions, and are often zinc metalloenzymes, containing a zinc cofactor.[2]
 Crystal structure of the open state of human endoplasmic reticulum aminopeptidase 1 ERAP1[1] | |||||||||
| Identifiers | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Symbol | Peptidase_M1 | ||||||||
| Pfam | PF01433 | ||||||||
| MEROPS | M1 | ||||||||
| OPM superfamily | 227 | ||||||||
| OPM protein | 3mdj | ||||||||
| CDD | cd09595 | ||||||||
| Membranome | 534 | ||||||||
| |||||||||
Aminopeptidases occur in both water-soluble and membrane-bound forms and can therefore be found in various cellular compartments as well as outside of cells.[3] Their broad substrate specificity, their ability to strongly bind to their targets, allows them to remove beginning N-terminal amino acids from almost all unsubstituted oligopeptides.[4] For instance, Aminopeptidase N (AP-N) is particularly abundant in the brush border membranes of the kidney, the small intestine, and the placenta, and is also found in the liver.[4] AP-N is involved in the final digestion of peptides generated from the cleaving and hydrolysis of proteins by gastric and pancreatic proteases.[5]
Some aminopeptidases are monomeric, or found by themselves, and others are found as assemblies of relatively high mass (50 kDa) subunits. cDNA sequences are available for several aminopeptidases and a crystal structure of the open state of human endoplasmic reticulum Aminopeptidase 1 ERAP1 is available.[1]
History
The discovery and characterization of aminopeptidases date back to the early 20th century. The term "aminopeptidase" was first introduced in 1929 by Linderstrøm-Lang and Sato in order to describe enzymes that cleave amino acids from the N-terminus of peptides.[6][better source needed]
In the 1950s and 1960s, the discovery of leucine aminopeptidase (LAP) and aminopeptidase N (APN) marked important milestones in the field. LAP was found to be crucial for protein digestion, while APN was recognized for its role in the regulation of peptide-mediated effects.[4][7] These discoveries were pivotal in understanding the physiological functions of aminopeptidases and their involvement in health and disease.[citation needed]
The subsequent decades[which?] saw extensive research into the structure, function, and mechanisms of action of various aminopeptidases. For example, the M1 family of aminopeptidases, which includes puromycin-sensitive aminopeptidase (PSA), was characterized by conserved zinc-dependent sites and exopeptidase motifs.[7][better source needed] The study of PSA in different model organisms revealed its essential roles in growth and behavior. Mutations in orthologs of PSA in different species were linked to errors in meiosis and reduced viability of embryos.[7] Aminopeptidase N, also known as AP-N or CD13, was extensively characterized for its broad substrate specificity (ability to bind to its targets) and its presence in various tissues such as the brush border membranes of the kidney, small intestine, and placenta.[4] The enzyme's role in brain function and its identification as the human cluster differentiation antigen CD13 on the surface of myeloid cells further highlighted its biological significance.[citation needed]
Classification and structure
Aminopeptidases are a diverse group of enzymes that play crucial roles in various biological processes, including protein digestion, cell growth, and immune response. They are classified based on their substrate specificity and catalytic mechanism into two main categories: metalloaminopeptidases and cysteine aminopeptidases.
Metalloaminopeptidases require metal ions, such as zinc or manganese, for their catalytic activity. These enzymes are characterized by a conserved HEXXH motif in their active site, which is involved in metal ion coordination. This motif is crucial for the catalytic function of the enzyme, as the histidine residues within the motif coordinate the metal ion, facilitating the hydrolysis of the peptide bond.[8] Metalloaminopeptidases are the largest and most homogenous class of aminopeptidases, with over 35 families identified within the MA clan according to the MEROPS database. This classification is based on structural similarities and evolutionary relationships, indicating a common ancestral origin for these enzymes,[8] Examples of metalloaminopeptidases include aminopeptidase N (APN), leucine aminopeptidase (LAP), and aminopeptidase A (APA).[9][10]
Cysteine aminopeptidases, on the other hand, rely on a catalytic cysteine residue for their activity. These enzymes are part of a broader group known as cysteine proteases, which share a common catalytic mechanism involving a nucleophilic cysteine thiol in a catalytic triad or dyad. The catalytic triad typically consists of cysteine, histidine, and aspartate residues, where the cysteine acts as a nucleophile, the histidine as a base, and the aspartate stabilizes the histidine.[11] Examples of cysteine aminopeptidases include cathepsin H and aminopeptidase B.[9]
The actual structure of aminopeptidases varies depending on the specific enzyme, but they generally consist of a catalytic domain and additional domains that contribute to substrate recognition and regulation. For instance, Aminopeptidase N (APN)/CD13, a type II metalloprotease, consists of 967 amino acids with a short N-terminal cytoplasmic domain, a single transmembrane part, and a large cellular ectodomain containing the active site.[9] The ectodomain is responsible for substrate binding and hydrolysis, highlighting the importance of domain organization in the function of aminopeptidases.[11]
Mechanisms
Aminopeptidases function as monozinc enzymes, where a zinc ion is crucial for their catalytic activity. The enzymatic mechanism involves the coordination of the zinc ion with water molecules and specific amino acid residues in the active site, enabling the hydrolysis of peptide bonds. Conserved residues and motifs within aminopeptidases significantly impact their catalytic efficiency and specificity. For instance, vertebrate aminopeptidases like aminopeptidase B contain evolutionarily conserved tyrosines essential for their enzymatic function. In aminopeptidase A (APA), residues Arg368 and Arg386 in the S2' subsite are vital for inhibitor binding and catalysis. These residues interact with APA inhibitors' P2' and P1' residues, enhancing inhibitory potency. The structural flexibility of aminopeptidases is critical for their catalytic mechanism. For example, ERAP1 displays distinct conformations, with domain IV's position relative to domain II affecting catalytic efficiency. Mutations disrupting interdomain interactions can reduce activity. IRAP exhibits active-site plasticity, accommodating various substrates through ligand-induced conformational changes that restrict solvent access to the catalytic center, showcasing its substrate permissiveness.
Production
Aminopeptidases are produced by a wide range of organisms, including bacteria, fungi, plants, and animals, and they serve essential roles in various biological processes.
In bacteria, aminopeptidases are produced by both facultative and obligate strains and can be found in different cellular locations such as the cytoplasm, membranes, associated with the cell envelope, or secreted into the extracellular media.[12] These enzymes are involved in the catabolism of exogenously supplied peptides and are necessary for the final steps of protein turnover. They also participate in specific functions like the cleavage of N-terminal methionine from newly synthesized peptide chains (methionine aminopeptidases), stabilization of multicopy ColE1 based plasmids (aminopeptidase A), and the cleavage of N-terminal pyroglutamate (pyroglutamyl aminopeptidase.[12]
Fungi, particularly species like Aspergillus oryzae and Aspergillus sojae, produce aminopeptidases that have applications in the food industry as debittering agents.[13] These enzymes are also of interest for their potential biotechnological applications. For example, leucine aminopeptidase (LAP) from Aspergillus species has been found to be thermostable and could be used to control the degree of hydrolysis and flavor development in a wide range of substrates.[13]
In mammals, aminopeptidases are produced in various tissues and organs, such as the liver, kidney, and intestine. They are involved in protein digestion, regulation of peptide-mediated effects, and the metabolism of bioactive peptides.[4] Aminopeptidase N (AP-N), also known as CD13, is particularly abundant in the brush border membranes of the kidney, small intestine, and placenta, and is also rich in the liver.[4] It has a broad substrate specificity and is involved in the final digestion of peptides generated from hydrolysis of proteins by gastric and pancreatic proteases.[4]
Biological role
Aminopeptidases play an important role in the metabolism of both proteins and peptides. Aminopeptidases in the gastrointestinal tract, such as APN and APA, are essential for the digestion of dietary proteins. They facilitate the absorption and utilization of amino acids by cleaving them from the N-terminus of peptides.[14] These enzymes also play a role in the metabolism of bioactive peptides, including hormones and growth factors. By regulating the levels of these peptides, aminopeptidases contribute to homeostasis and physiological process modulation.[14]
Biotechnology
Edman degradation
In protein sequencing, aminopeptidases are employed in the Edman degradation method. This technique involves the sequential removal and identification of the N-terminal amino acid of proteins, facilitating the elucidation of their amino acid sequence.[15]
Biosensors
Aminopeptidases have been utilized in creating biosensors for detecting specific amino acids or peptides. These biosensors generate a measurable signal in the presence of the target analyte, leveraging the catalytic activity of aminopeptidases.[14]
Medical uses
Aminopeptidase has been studied for use in treating hypertension, inflammation, and some cancers. Aminopeptidase A (APA) is implicated in blood pressure regulation by converting angiotensin II to angiotensin III. APA inhibitors are being explored as potential antihypertensive agents, offering a novel approach to managing hypertension.[14] Aminopeptidase N (APN) has been associated with the pathogenesis of inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease. Inhibitors of APN have demonstrated anti-inflammatory effects in animal models, positioning them as potential therapeutic agents for these conditions.[14] Several aminopeptidases, including APN, APA, and leucine aminopeptidase (LAP), are overexpressed in various cancers. Their involvement in tumor growth, invasion, and angiogenesis makes them attractive targets for cancer therapy. Aminopeptidase inhibitors have shown promise in preclinical studies as potential anticancer agents.[14]
As diagnostic markers
The activity and expression levels of aminopeptidases have been explored as diagnostic markers for diseases like liver disorders and cancer. Variations in these parameters can indicate pathological conditions, aiding in disease diagnosis and monitoring.[14]
Food industry
In the food industry, aminopeptidases from Aspergillus oryzae and Aspergillus sojae are utilized for debittering protein hydrolysates, including those used in soy sauce and miso production. These enzymes help remove bitter-tasting peptides, enhancing the flavor and palatability of these products.[15] Aminopeptidases also play a crucial role in cheese ripening by participating in the proteolysis of milk proteins. This enzymatic action contributes significantly to the development of the cheese's flavor and texture, making aminopeptidases essential in the cheese-making process.[15]
When aminopeptidases are used in food processing, it is crucial to ensure that they are food-grade and safe for consumption. Aminopeptidases from A. oryzae and A. sojae, for example, have been extensively studied and are considered safe for use in food applications.[16] It is important to handle these enzymes under conditions that prevent contamination and degradation, which could affect both the safety and quality of the food products.
Aminopeptidases require specific storage conditions to maintain their stability and enzymatic activity. For instance, human aminopeptidase A is stable at a pH range of 7.0-8.5 and can be stored at -20°C for several months without significant loss of activity. Similarly, a halotolerant intracellular protease from Bacillus subtilis strain FP-133, which exhibits aminopeptidase activity, retains full activity after being stored in 7.5% (w/v) NaCl at 4°C for 24 hours.[17] These examples indicate that aminopeptidases generally require neutral pH conditions and can be stored at low temperatures, such as -20°C or -80°C, for extended periods to preserve their activity.
See also
References
- ^ a b PDB: 3QNF: Kochan G, Krojer T, Harvey D, Fischer R, Chen L, Vollmar M, von Delft F, Kavanagh KL, Brown MA, Bowness P, Wordsworth P, Kessler BM, Oppermann U (May 2011). "Crystal structures of the endoplasmic reticulum aminopeptidase-1 (ERAP1) reveal the molecular basis for N-terminal peptide trimming". Proceedings of the National Academy of Sciences of the United States of America. 108 (19): 7745–50. Bibcode:2011PNAS..108.7745K. doi:10.1073/PNAS.1101262108. PMC 3093473. PMID 21508329.
- ^ Taylor, A (February 1993). "Aminopeptidases: structure and function". FASEB Journal. 7 (2): 290–8. doi:10.1096/fasebj.7.2.8440407. PMID 8440407. S2CID 23354720.
- ^ Bradshaw, R.A. (2013), "Aminopeptidases", Encyclopedia of Biological Chemistry, Elsevier, pp. 97–99, doi:10.1016/b978-0-12-378630-2.00002-5, ISBN 978-0-12-378631-9, retrieved 2024-03-20
- ^ a b c d e f g Turner, Anthony J. (2013), "Aminopeptidase N", Handbook of Proteolytic Enzymes, Elsevier, pp. 397–403, doi:10.1016/b978-0-12-382219-2.00079-x, ISBN 978-0-12-382219-2, retrieved 2024-03-20
- ^ Sanz, Yolanda (2007), "Aminopeptidases", Industrial Enzymes, Dordrecht: Springer Netherlands, pp. 243–260, doi:10.1007/1-4020-5377-0_15, ISBN 978-1-4020-5376-4, retrieved 2024-03-20
- ^ Bala, Sandeep Chowdary; Haque, Neshatul; Pillalamarri, Vijaykumar; Reddi, Ravikumar; Kashyap, Rajnandani; Marapaka, Anil Kumar; Addlagatta, Anthony (2019-05-15). "Discovery of a new class of type 1 methionine aminopeptidases that have relaxed substrate specificity". International Journal of Biological Macromolecules. 129: 523–529. doi:10.1016/j.ijbiomac.2019.02.055. ISSN 0141-8130. PMID 30763644. S2CID 73436841.
- ^ a b c Su, Shanchun; Pan, Baoliang; Hu, Yanxin; Wang, Ming (2019-11-12). "Characterization of aminopeptidase encoding gene anp-1 and its association with development in Caenorhabditis elegans". PeerJ. 7: e7944. doi:10.7717/peerj.7944. ISSN 2167-8359. PMC 6857582. PMID 31737443.
- ^ a b Mucha, Artur; Drag, Marcin; Dalton, John P.; Kafarski, Paweł (November 2010). "Metallo-aminopeptidase inhibitors". Biochimie. 92 (11): 1509–1529. doi:10.1016/j.biochi.2010.04.026. ISSN 0300-9084. PMC 7117057. PMID 20457213. S2CID 37896195.
- ^ a b c Luan, Yepeng; Xu, Wenfang (2007-03-01). "The Structure and Main Functions of Aminopeptidase N". Current Medicinal Chemistry. 14 (6): 639–647. doi:10.2174/092986707780059571. ISSN 0929-8673. PMID 17346152.
- ^ Silbernagl, Stefan; Gekle, Michael (2008), "Amino Acids, Oligopeptides, and Hyperaminoacidurias", Seldin and Giebisch's The Kidney, Elsevier, pp. 2021–2044, doi:10.1016/b978-012088488-9.50075-9, ISBN 978-0-12-088488-9, retrieved 2024-03-20
- ^ a b Turk, Vito; Stoka, Veronika; Vasiljeva, Olga; Renko, Miha; Sun, Tao; Turk, Boris; Turk, Dušan (January 2012). "Cysteine cathepsins: From structure, function and regulation to new frontiers". Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics. 1824 (1): 68–88. doi:10.1016/j.bbapap.2011.10.002. ISSN 1570-9639. PMC 7105208. PMID 22024571. S2CID 205851962.
- ^ a b Gonzales, Thierry; Robert-Baudouy, Janine (July 1996). "Bacterial aminopeptidases: Properties and functions". FEMS Microbiology Reviews. 18 (4): 319–344. doi:10.1111/j.1574-6976.1996.tb00247.x. ISSN 0168-6445. PMID 8703509.
- ^ a b Nampoothiri, K.M.; Nagy, V.; Kovacs, K.; Szakacs, G.; Pandey, A. (December 2005). "l-leucine aminopeptidase production by filamentous Aspergillus fungi". Letters in Applied Microbiology. 41 (6): 498–504. doi:10.1111/j.1472-765x.2005.01789.x. ISSN 0266-8254. PMID 16305677.
- ^ a b c d e f g Nandan, Arya; Nampoothiri, Kesavan Madhavan (2020-04-28). "Therapeutic and biotechnological applications of substrate specific microbial aminopeptidases". Applied Microbiology and Biotechnology. 104 (12): 5243–5257. doi:10.1007/s00253-020-10641-9. ISSN 0175-7598. PMC 7186005. PMID 32342144.
- ^ a b c Wang, Yawei; Zhao, Puying; Zhou, Ying; Hu, Xiaomin; Xiong, Hairong (2023-01-10). "From bitter to delicious: properties and uses of microbial aminopeptidases". World Journal of Microbiology and Biotechnology. 39 (3): 72. doi:10.1007/s11274-022-03501-3. ISSN 0959-3993. PMID 36625962.
- ^ Adam Salifou; Christian Tétédé Rodrigue Konfo; Alexandrine Bokossa; Nicodème Worou Chabi; Fidèle Paul Tchobo; Mohamed Mansourou Soumanou (2023-11-30). "Innovative approaches in food processing: enhancing quality, preservation, and safety through advanced technologies: A review". World Journal of Advanced Research and Reviews. 20 (2): 637–648. doi:10.30574/wjarr.2023.20.2.2297. ISSN 2581-9615.
- ^ Setyorini, Endang; Kim, Young-Ju; Takenaka, Shinji; Murakami, Shuichiro; Aoki, Kenji (2006-07-17). "Purification and characterization of a halotolerant intracellular protease from Bacillus subtilis strain FP-133". Journal of Basic Microbiology. 46 (4): 294–304. doi:10.1002/jobm.200510086. ISSN 0233-111X. PMID 16847833.
External links
- Aminopeptidases at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- Mechanism of aminopeptidase
