Puromycin-sensitive amino peptidase also known as cytosol alanyl aminopeptidase or alanine aminopeptidase (AAP) (EC3.4.11.14) is an enzyme that in humans is encoded by the NPEPPSgene.[5][6][7] It is used as a biomarker to detect damage to the kidneys, and that may be used to help diagnose certain kidney disorders. It is found at high levels in the urine when there are kidney problems.[8]
This gene encodes the puromycin-sensitive aminopeptidase, a zinc metallopeptidase which hydrolyzes amino acids from the N-terminus of its substrate. The protein has been localized to both the cytoplasm and to cellular membranes. This enzyme degrades enkephalins in the brain, and studies in mouse suggest that it is involved in proteolytic events regulating the cell cycle.[7] It has been identified as a novel modifier of TAU-induced neurodegeneration with neuroprotective effects via direct proteolysis of TAU protein.[9][10] The loss of NPEPPS function exacerbates neurodegeneration.[11]
NPEPPS is a ubiquitous, 100 kDa, Zn2+metallopeptidase highly expressed in the brain.[12] Two isozymes have been found and they are expressed differently in the nervous system.[13]Glu 309 is one of the active site glutamates, and its mutation could convert the enzyme into an inactive binding protein.[14]
NPEPPS has been proposed to function in a variety of processes, including metabolism of neuropeptidase, regulation of the cell cycle, and hydrolysis of proteasomal products to amino acids.[15][16][17] NPEPPS is a major protease to digest SOD1, similar to its role in TAU-induced neurodegeneration.[10][18] NPEPPS is also reported to play a role in creating and destroying MHC class I-presented peptides and in limiting MHC class I Ag presentation in dendritic cells.[19]
NPEPPS is induced in neurons expressing mutant huntingtin and is critical in preventing the accumulation of polyglutamine in normal cells. It has been reported as the major peptidase digesting polyglutamine sequences in neurodegenerative diseases, such as Huntington's disease.[20] It has been shown that elevation of NPEPPS activity in vivo could effectively block accumulation of hyperphosphorylated TAU protein and thus slow down the disease progression, suggesting increasing NPEPPS activity may be a feasible therapeutic approach to eliminate accumulation of toxic substrates, which are involved in neurodegenerative diseases.[21]
^Thompson MW, Tobler A, Fontana A, Hersh LB (May 1999). "Cloning and analysis of the gene for the human puromycin-sensitive aminopeptidase". Biochemical and Biophysical Research Communications. 258 (2): 234–40. doi:10.1006/bbrc.1999.0604. PMID10329370.
^Holdt B, Peters E, Nagel HR, Steiner M (2008). "An automated assay of urinary alanine aminopeptidase activity". Clinical Chemistry and Laboratory Medicine. 46 (4): 537–40. doi:10.1515/CCLM.2008.103. PMID18302530. S2CID45057277.
^Sengupta S, Horowitz PM, Karsten SL, Jackson GR, Geschwind DH, Fu Y, Berry RW, Binder LI (December 2006). "Degradation of tau protein by puromycin-sensitive aminopeptidase in vitro". Biochemistry. 45 (50): 15111–9. doi:10.1021/bi061830d. PMID17154549.
^Rawson NS (November 2009). "Access to linked administrative healthcare utilization data for pharmacoepidemiology and pharmacoeconomics research in Canada: anti-viral drugs as an example". Pharmacoepidemiology and Drug Safety. 18 (11): 1072–9. doi:10.1002/pds.1822. PMID19650154. S2CID22999576.
^Thompson MW, Govindaswami M, Hersh LB (May 2003). "Mutation of active site residues of the puromycin-sensitive aminopeptidase: conversion of the enzyme into a catalytically inactive binding protein". Archives of Biochemistry and Biophysics. 413 (2): 236–42. doi:10.1016/s0003-9861(03)00123-1. PMID12729622.
^Aeluri R, Ganji RJ, Marapaka AK, Pillalamarri V, Alla M, Addlagatta A (December 2015). "Highly functionalized tetrahydropyridines are cytotoxic and selective inhibitors of human puromycin sensitive aminopeptidase". European Journal of Medicinal Chemistry. 106: 26–33. doi:10.1016/j.ejmech.2015.10.026. PMID26513642.
Bauer WO, Nanda I, Beck G, Schmid M, Jakob F (2001). "Human puromycin-sensitive aminopeptidase: cloning of 3' UTR, evidence for a polymorphism at a.a. 140 and refined chromosomal localization to 17q21". Cytogenetics and Cell Genetics. 92 (3–4): 221–4. doi:10.1159/000056907. PMID11435692. S2CID28906058.
de Gandarias JM, Irazusta J, Gil J, Fernández D, Varona A, Casis L (November 1999). "Ontogeny of puromycin-sensitive and insensitive aminopeptidase activities in several subcellular fractions of the rat brain". Brain Research Bulletin. 50 (4): 283–90. doi:10.1016/S0361-9230(99)00189-6. PMID10582526. S2CID6673357.
McLellan S, Dyer SH, Rodriguez G, Hersh LB (November 1988). "Studies on the tissue distribution of the puromycin-sensitive enkephalin-degrading aminopeptidases". Journal of Neurochemistry. 51 (5): 1552–9. doi:10.1111/j.1471-4159.1988.tb01124.x. PMID3171591. S2CID20808131.
