Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Progressive cerebral deposition of the amyloid beta-peptide (Abeta) is an early and constant feature of Alzheimer's disease. Abeta is derived by proteolysis from the beta-amyloid precursor protein. beta-Amyloid precursor protein processing and the generation of Abeta have been extensively characterized, but little is known about the mechanisms of degradation of this potentially neurotoxic peptide. We identified and purified a proteolytic activity in culture medium that can degrade secreted Abeta but not larger proteins in the medium. Detection of the activity in conditioned medium required the presence of fetal bovine serum and the passage of the cells with a pancreatic trypsin preparation. Its inhibitor profile showed that the activity was a serine protease other than trypsin or chymotrypsin. The protease occurs as a stable approximately 700-kDa complex with the inhibitor, alpha2-macroglobulin (alpha2M), that retains activity against small substrates such as Abeta. Its NH2-terminal sequence suggests that the protease is previously unidentified. Our results indicate that the Abeta-degrading protease we have detected is a non-trypsin component of a pancreatic trypsin preparation or else derives from a zymogen in serum that is activated by a protease in the latter preparation. Because Abeta-bearing plaques in Alzheimer's disease brain contain both alpha2M and receptors of alpha2M-protease complexes, the same or a similar alpha2M-protease complex could arise in vivo and play a role in Abeta clearance.
...
PMID:Degradation of amyloid beta-protein by a serine protease-alpha2-macroglobulin complex. 862 44

A novel cDNA, IA-2beta, was isolated from a mouse neonatal brain library. The predicted protein sequence revealed an extracellular domain, a transmembrane region, and an intracellular domain. The intracellular domain is 376 amino acids long and 74% identical to the intracellular domain of IA-2, a major autoantigen in insulin-dependent diabetes mellitus (IDDM). A partial sequence of the extracellular domain of IA-2beta indicates that it differs substantially (only 26% identical) from that of IA-2. Both molecules are expressed in islets and brain tissue. Forty-six percent (23 of 50) of the IDDM sera but none of the sera from normal controls (0 of 50) immunoprecipitated the intracellular domain of IA-2beta. Competitive inhibition experiments showed that IDDM sera have autoantibodies that recognize both common and distinct determinants on IA-2 and IA-2beta. Many IDDM sera are known to immunoprecipitate 37-kDa and 40-kDa tryptic fragments from islet cells, but the identity of the precursor protein(s) has remained elusive. The current study shows that treatment of recombinant IA-2beta and IA-2 with trypsin yields a 37-kDa fragment and a 40-kDa fragment, respectively, and that these fragments can be immunoprecipitated with diabetic sera. Absorption of diabetic sera with unlabeled recombinant IA-2 or IA-2beta, prior to incubation with radiolabeled 37-kDa and 40-kDa tryptic fragments derived from insulinoma or glucagonoma cells, blocks the immunoprecipitation of both of these radiolabeled tryptic fragments. We conclude that IA-2beta and IA-2 are the precursors of the 37-kDa and 40-kDa islet cell autoantigens, respectively, and that both IA-2 and IA-2beta are major autoantigens in IDDM.
...
PMID:Identification of a second transmembrane protein tyrosine phosphatase, IA-2beta, as an autoantigen in insulin-dependent diabetes mellitus: precursor of the 37-kDa tryptic fragment. 863 68

Locally grown kumara (sweet potato; Ipomea batatis) was used as the starting point for the purification of a proteinase inhibitor. The purified inhibitor was highly specific for trypsin, and much less effective as an inhibitor of chymotrypsin. Two 22kDa variants were present, closely homologous to each other and to sporamin A, but with a single amino acid substitution (proline in place of serine, the second residue in mature sporamin A). One variant had the same N-terminus as sporamin A, whereas the other had a tripeptide N-terminal extension, which may represent an intermediate in the proteolytic processing of the precursor protein. A larger variant was apparently a disulphide-linked dimer of the monomeric inhibitor. A rabbit polyclonal antiserum prepared against the trypsin inhibitor reacted with all of these variants, but did not cross-react with commercially-available soybean proteinase inhibitors. The purified inhibitor did resemble other proteinase inhibitors in having a biphasic effect upon the proliferation of human fibroblasts, with a mitogenic action at low concentrations, and an inhibitory effect at higher concentrations.
...
PMID:Isolation, characterisation and cell growth-regulatory properties of kumara (sweet potato) trypsin inhibitors. 885 May 29

The primary structure of beta 2-microglobulin (beta 2m), the major constituent protein of beta 2-microglobulin amyloidosis (A beta 2m) or dialysis-amyloidosis, was initially shown to be identical to serum beta 2m, thereby strongly suggesting the polymerization of intact beta 2m in tissues. Recent biochemical data have been controversial, showing beta 2m acidic isoforms, fragmentation and amino acid sequence alteration of deposited beta 2m. The aim of this study was to reinvestigate beta 2m amyloid deposits for the presence of beta 2m fragments and/or amino acid sequence alteration. Four amyloid-laden tissues (3 femoral bone amyloid cysts and 1 heart tissue) from dialysis patients were used to isolate amyloidogenic beta 2m. Amyloid fibrils were isolated using the classic water extraction method, and purified in 6 M guanidine on a gel-filtration column. The protein was further purified on 17% SDS-PAGE gel, and transferred to a nitrocellulose membrane for immunostaining with antihuman beta 2m. beta 2m samples were microsequenced using the standard 03RPTH program on a 470A gas-phase sequencer, and HPLC was performed after digestion with trypsin. Two peaks were obtained with the gel filtration column, the second corresponding by molecular weight to beta 2m. SDS-PAGE analysis of this peak under reducing conditions, demonstrated one major band at 12,000 Da and a minor band at 25,000 Da (monomer and dimer), and no lower molecular weight bands were observed. The 12 kDa band was micro-sequenced and the amino acid sequence corresponded to that of normal beta 2m through the 40th residue. Amino acid sequence analysis showed no difference from normal beta 2m in any of the beta 2m proteins contained in the amyloid deposits isolated from the four studied tissues. Also, the HPLC profile of the four protein samples were strictly normal and identical to a commercial preparation of beta 2m. The present study demonstrates that beta 2m molecules polymerized in amyloid fibrils and deposits are intact and have a normal amino acid sequence, and produced by a specific and unique fibrillogenetic mechanism, which does not require proteolytic processing from the precursor protein to the amyloid fibrils.
...
PMID:Polymerization of normal and intact beta 2-microglobulin as the amyloidogenic protein in dialysis-amyloidosis. 888 86

Human lactase-phlorizin hydrolase (EC 3.2.1.23/62) is a major disaccharidase in the microvillus membrane of small intestinal epithelial cells. The enzyme is synthesized as a single-chain precursor protein and undergoes proteolytic processing during maturation. We studied proteolytic processing of human lactase-phlorizin hydrolase in transfected COS-1, Caco-2, and MDCK cells using metabolic labeling, surface immunoprecipitation, protease sensitivity assays, and microsequencing. Furthermore, we generated mutated forms of the enzyme to alter potential proteolytic cleavage sites and expressed these in Caco-2 and COS-1 cells. Since the N-terminal amino acid of microvillus lactase-phlorizin hydrolase corresponds to Ala869 in the precursor protein, it has been speculated that processing occurs at position Arg868-Ala869. Substitution of Arg868 with isoleucine, lysine, or glutamic acid had no effect on the proteolytic processing of pro-LPH in Caco-2 cells. As in wild-type enzyme a processed 160-kDa form was generated. These data are not consistent with a primary proteolytic processing at position Arg868-Ala869. Using amino-terminal amino acid sequencing of this processed form isolated from stable transfected MDCK cells we identified the cleavage site at Arg734-Leu735. Treatment of pro-lactase-phlorizin hydrolase expressed in COS-1 and MDCK cells by trypsin yielded a 145-kDa form with an identical amino terminal as the mature microvillus enzyme isolated from intestinal mucosa (Ala869). These data provide unambiguous evidence of a two-step processing of human lactase-phlorizin hydrolase. The first cleavage occurs intracellularly after a dibasic site (Arg734-Leu735) and yields the 160-kDa intermediate form. In a second step the intermediate form inserted into the microvillus membrane is trimmed to the mature enzyme by luminal trypsin.
...
PMID:Proteolytic processing of human lactase-phlorizin hydrolase is a two-step event: identification of the cleavage sites. 895 Oct 31

The cornified envelope (CE) is an insoluble sheath of epsilon-(gamma-glutamyl)lysine cross-linked protein, which is deposited beneath the plasma membrane during keratinocyte terminal differentiation. We have probed the structure of the CE by proteolytic cleavage of purified CE fragments isolated from CEs formed spontaneously in cell culture. CNBr digestion, followed by trypsin and then proteinase K treatment released 25%, 42%, and 18%, respectively, of the CE protein. Purification and sequencing of released peptides has identified two novel CE precursors, S100A11 (S100C, calgizzarin) and S100A10 (calpactin light chain). We also sequenced peptides derived from annexin I and plasminogen activator inhibitor 2, two putative envelope precursors, as well as portions of the well established CE precursor proteins SPR1A, SPR1B, and involucrin. Many desmosomal components were identified (desmoglein 3, desmocolin A/B, desmoplakin I, plakoglobin, and plakophilin), indicating that desmosomes become cross-linked into the CE. Fragments derived from envoplakin, the recently sequenced 210-kDa membranous CE precursor protein, which also appears to be a desmosomal component, were also identified. Analysis of the pattern of peptide release following the sequential digestion indicates that S100A11 is anchored to the envelope via Gln102 and/or Lys103 at the carboxyl terminus and at Lys3, Lys23, and/or Gln22 in the amino terminus. A similar type of analysis indicates that small proline-rich proteins 1A and 1B (SPR1A and SPR1B) become cross-linked at the amino terminus (residues 1-23) and the carboxyl terminus (residues 86-89). No loricrin, cystatin A, or elafin peptides were detected.
...
PMID:S100A11, S100A10, annexin I, desmosomal proteins, small proline-rich proteins, plasminogen activator inhibitor-2, and involucrin are components of the cornified envelope of cultured human epidermal keratinocytes. 911 70

Most mitochondrial proteins are nuclear encoded, synthesized on cytosolic ribosomes, and imported into the mitochondria. We have identified and characterized a 309 amino acid human protein with a molecular weight of 34 kDa that functions as a subunit of the translocase for the import of such proteins. hTom34 (34-kDa Translocase of the Outer Mitochondrial Membrane) is displayed on the surface of mitochondria and is resistant to extraction under alkaline conditions. Antibodies raised against hTom34 specifically inhibit in vitro import of the mitochondrial precursor protein preornithine transcarbamylase into mitochondria isolated from rat liver. Based on trypsin digestion experiments, the receptor has a large (27 kDa) C-terminal domain exposed to the cytosol. This novel component of the protein import machinery possesses a 62 residue motif conserved with the Tom70 family of mitochondrial receptors but otherwise appears to have no counterpart so far characterized in the mitochondria of any other species.
...
PMID:hTom34: a novel translocase for the import of proteins into human mitochondria. 932 9

We recently identified a cDNA encoding a human brain specific trypsinogen (trypsinogen IV). In order to test whether trypsinogen IV is involved in CNS diseases of, or injury response in, mammalian brain, a mouse model was developed in which the human trypsinogen IV was expressed specifically in neurons. Immunocytochemical analysis of the brains of transgenic mice revealed a striking enhancement of glial fibrillar acidic protein (GFAP) expression in astrocytes. This remarkable astrocytic reaction was detected in the brains of mice as young as 2 months and did not diminish in the older animals we tested. However, we did not find gross evidence for neurodegeneration, nor for reactive microglial cells. The long-term survival of these animals should provide a model with which to study the mechanism of nerve-astroglia interactions. In addition, the possible participation of trypsin IV in the metabolism of the Alzheimer precursor protein (APP) was investigated by immunostaining brains from transgenic mice with beta-amyloid (betaA4) antibodies. Immunocytochemical staining of brains from one year old transgenic mice revealed an intense intracellular betaA4-like signal in neurons.
...
PMID:Enhanced GFAP expression in astrocytes of transgenic mice expressing the human brain-specific trypsinogen IV. 951 66

Acylation stimulating protein (ASP) is a potent stimulator of adipocyte triacylglycerol storage. In vivo studies have shown that ASP production by adipocytes increases locally after a fat meal. Initial in vitro studies demonstrated increased production of ASP in the presence of chylomicrons (CHYLO). The present aim was to define the CHYLO component responsible. None of the apoproteins tested (AI, AII, AIV, CI, CII, CIII, and E) were capable of stimulating C3 (the precursor protein) or ASP production. Rather, the active component is a nonlipid, loosely associated, trypsin-sensitive molecule. High pressure liquid chromatography fractionation of the CHYLO infranate proteins identified the critical protein as transthyretin (TTR), which binds retinol-binding protein and complexes thyroxine and retinol. Addition of TTR alone, with lipid emulsion, or with respun CHYLO to human differentiated adipocytes had little effect on C3 and ASP production. By contrast, when transthyretin was added to CHYLO, C3 and ASP production were substantially enhanced up to 75- and 7. 5-fold respectively, compared with the effect of native CHYLO alone. Finally, a polyclonal antibody against TTR could inhibit stimulation of C3 and ASP production by CHYLO (by 98 and 100%, respectively) and by CHYLO infranate proteins (by 99 and 94%, respectively). We hypothesize that TTR mediates the transfer of the active components from CHYLO to adipocytes, which then stimulates increased C3 and ASP production. Thus the CHYLO provides the physiologic trigger of the ASP pathway.
...
PMID:Chylomicron-specific enhancement of acylation stimulating protein and precursor protein C3 production in differentiated human adipocytes. 969 37

We have isolated from mouse intestine a full-length cDNA clone that encodes an 86-amino acid precursor protein containing a 26-amino acid signal sequence. As deduced from its sequence, the mature 60-aa protein named MPGC60 belongs to the Kazal type of secreted trypsin inhibitors. The MPGC60 peptide has 58% homology with the PEC-60 peptide isolated from pig intestine. In the gut of adult mice, an increasing rostrocaudal gradient in MPGC60 mRNA levels was observed by Northern analysis. In situ hybridization analysis demonstrated strong Mpgc60 expression in Paneth cells and in a subset of goblet cells in the differentiated gut. During postnatal differentiation of the gut, a strong increase in Mpgc60 expression was detected in both small and large intestine. However, in small intestine activation of the Mpgc60 gene occurred earlier than in the large intestine. Apart from the intestinal tract, MPGC60 mRNA was also detectable in the mesenchyme surrounding the uterine epithelium and in endothelia of some blood vessels. However, in contrast to the situation observed in pig, no Mpgc60 expression was detectable by Northern, in situ and reverse transcriptase polymerase chain reaction (RT-PCR) analysis in cells of the immune system, that is, in monocytes, macrophages, peripheral blood and in spleen. Northern blot analysis on mRNA isolated from porcine and murine intestine showed a single transcript in mouse, but several transcripts in pig. Southern blot and fluorescent in situ hybridisation (FISH) analysis demonstrated the presence of a single gene situated in band A of chromosome 4. This region is syntenic with human chromosome regions 6q, 8q and 9p. The gene responsible for human hereditary mixed polyposis syndrome has been localized to human 6q. This raises the possibility that Mpgc60 is a candidate gene for this human disorder.
...
PMID:Molecular cloning and characterization of murine Mpgc60, a gene predominantly expressed in the intestinal tract. 981 Jul 7


<< Previous 1 2 3 4 5 6 7 8 9 Next >>

---