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Proinsulin is the prohormone precursor to insulin made in the beta cells of the Pancreatic Islets, specialized regions of the pancreas. In humans, proinsulin is encoded by the INS gene. The pancreatic islets only secrete between 1% and 3% of proinsulin intact. However, because proinsulin has a longer half life than insulin, it can account for anywhere from 5–30% of the insulin-like structures circulating in the blood. There are higher concentrations of proinsulin after meals and lower levels when a person is fasting. Additionally, while proinsulin and insulin have structural differences, proinsulin does demonstrate some affinity for the insulin receptor. Due to the relative similarities in structure, proinsulin can produce between 5% and 10% of the metabolic activity similarly induced by insulin.
Ornithine transcarbamylase (OTC) is an enzyme that catalyzes the reaction between carbamoyl phosphate (CP) and ornithine (Orn) to form citrulline (Cit) and phosphate (Pi). There are two classes of OTC: anabolic and catabolic. This article focuses on anabolic OTC. Anabolic OTC facilitates the sixth step in the biosynthesis of the amino acid arginine in prokaryotes. In contrast, mammalian OTC plays an essential role in the urea cycle, the purpose of which is to capture toxic ammonia and transform it into urea, a less toxic nitrogen source, for excretion.
Malate dehydrogenase (EC 1.1.1.37) (MDH) is an enzyme that reversibly catalyzes the oxidation of malate to oxaloacetate using the reduction of NAD+ to NADH. This reaction is part of many metabolic pathways, including the citric acid cycle. Other malate dehydrogenases, which have other EC numbers and catalyze other reactions oxidizing malate, have qualified names like malate dehydrogenase (NADP+).
Furin is a protease, a proteolytic enzyme that in humans and other animals is encoded by the FURIN gene. Some proteins are inactive when they are first synthesized, and must have sections removed in order to become active. Furin cleaves these sections and activates the proteins. It was named furin because it was in the upstream region of an oncogene known as FES. The gene was known as FUR and therefore the protein was named furin. Furin is also known as PACE. A member of family S8, furin is a subtilisin-like peptidase.
Proprotein convertases (PPCs) are a family of proteins that activate other proteins. Many proteins are inactive when they are first synthesized, because they contain chains of amino acids that block their activity. Proprotein convertases remove those chains and activate the protein. The prototypical proprotein convertase is furin. Proprotein convertases have medical significance, because they are involved in many important biological processes, such as cholesterol synthesis. Compounds called proprotein convertase inhibitors can block their action, and block the target proteins from becoming active. Many proprotein convertases, especially furin and PACE4, are involved in pathological processes such as viral infection, inflammation, hypercholesterolemia, and cancer, and have been postulated as therapeutic targets for some of these diseases.
Cholesterol side-chain cleavage enzyme is commonly referred to as P450scc, where "scc" is an acronym for side-chain cleavage. P450scc is a mitochondrial enzyme that catalyzes conversion of cholesterol to pregnenolone. This is the first reaction in the process of steroidogenesis in all mammalian tissues that specialize in the production of various steroid hormones.
Met-enkephalin, also known as metenkefalin (INN), sometimes referred to as opioid growth factor (OGF), is a naturally occurring, endogenous opioid peptide that has opioid effects of a relatively short duration. It is one of the two forms of enkephalin, the other being leu-enkephalin. The enkephalins are considered to be the primary endogenous ligands of the δ-opioid receptor, due to their high potency and selectivity for the site over the other endogenous opioids.
In enzymology, a pyrroline-5-carboxylate reductase (EC 1.5.1.2) is an enzyme that catalyzes the chemical reaction
The enzyme ornithine cyclodeaminase catalyzes the chemical reaction
Diphosphomevalonate decarboxylase (EC 4.1.1.33), most commonly referred to in scientific literature as mevalonate diphosphate decarboxylase, is an enzyme that catalyzes the chemical reaction
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, arginine kinase is an enzyme that catalyzes the chemical reaction
Nardilysin is a protein that in humans is encoded by the NRD1 gene.
Dipeptidyl peptidase I is an enzyme. This enzyme catalyses the following chemical reaction
Mannosyl-oligosaccharide 1,2-α-mannosidase (EC 3.2.1.113, mannosidase 1A, mannosidase 1B, 1,2-α-mannosidase, exo-α-1,2-mannanase, mannose-9 processing α-mannosidase, glycoprotein processing mannosidase I, mannosidase I, Man9-mannosidase, ManI, 1,2-α-mannosyl-oligosaccharide α-D-mannohydrolase) is an enzyme with systematic name 2-α-mannosyl-oligosaccharide α-D-mannohydrolase. It catalyses the hydrolysis of the terminal (1→2)-linked α-D-mannose residues in the oligo-mannose oligosaccharide Man9(GlcNAc)2.
Aminopeptidase B is an enzyme. This enzyme catalyses the following chemical reaction
Lysyl endopeptidase is an enzyme. This enzyme catalyses the following chemical reaction
Peptidyl-Asp metalloendopeptidase is an enzyme. This enzyme catalyses the following chemical reaction
Magnolysin is an enzyme. This enzyme catalyses the following chemical reaction
Endothelin-converting enzyme 1 is an enzyme. This enzyme catalyses the following chemical reaction
References
- ↑ Gomez S, Gluschankof P, Morel A, Cohen P (September 1985). "The somatostatin-28 convertase of rat brain cortex is associated with secretory granule membranes". The Journal of Biological Chemistry. 260 (19): 10541–5. doi: 10.1016/S0021-9258(19)85118-9 . PMID 3897221.
- ↑ Gluschankof P, Gomez S, Morel A, Cohen P (July 1987). "Enzymes that process somatostatin precursors. A novel endoprotease that cleaves before the arginine-lysine doublet is involved in somatostatin-28 convertase activity of rat brain cortex". The Journal of Biological Chemistry. 262 (20): 9615–20. doi: 10.1016/S0021-9258(18)47978-1 . PMID 2885328.
- ↑ Chesneau V, Pierotti AR, Barré N, Créminon C, Tougard C, Cohen P (January 1994). "Isolation and characterization of a dibasic selective metalloendopeptidase from rat testes that cleaves at the amino terminus of arginine residues". The Journal of Biological Chemistry. 269 (3): 2056–61. doi: 10.1016/S0021-9258(17)42134-X . PMID 8294457.
- ↑ Pierotti AR, Prat A, Chesneau V, Gaudoux F, Leseney AM, Foulon T, Cohen P (June 1994). "N-arginine dibasic convertase, a metalloendopeptidase as a prototype of a class of processing enzymes". Proceedings of the National Academy of Sciences of the United States of America. 91 (13): 6078–82. Bibcode:1994PNAS...91.6078P. doi: 10.1073/pnas.91.13.6078 . PMC 44141 . PMID 8016118.
