Structure of puromycin-sensitive aminopeptidase and polyglutamine binding.

Puromycin-sensitive aminopeptidase (E.C. 3.

Analysis of circulating metabolites to differentiate Parkinson's disease and essential tremor.

Parkinson's disease (PD) and essential tremor (ET) are two common adult-onset tremor disorders in which prevalence increases with age. PD is a neurodegenerative condition with progressive disability. In ET, neurodegeneration is not an established etiology.

Changes in the gray and white matter of patients with ischemic-edematous insults after traumatic brain injury.

Objective: Gray matter (GM) and white matter (WM) are vulnerable to ischemic-edematous insults after traumatic brain injury (TBI). The extent of secondary insult after brain injury is quantifiable using quantitative CT analysis. One conventional quantitative CT measure, the gray-white matter ratio (GWR), and a more recently proposed densitometric analysis are used to assess the extent of these insults.

Parkinson's disease and multiple system atrophy have distinct α-synuclein seed characteristics.

Parkinson's disease (PD) and multiple system atrophy (MSA) are distinct clinical syndromes characterized by the pathological accumulation of α-synuclein (α-syn) protein fibrils in neurons and glial cells. These disorders and other neurodegenerative diseases may progress via prion-like mechanisms. The prion model of propagation predicts the existence of "strains" that link pathological aggregate structure and neuropathology.

Insulin-degrading enzyme is not secreted from cultured cells.

Insulin-degrading enzyme (IDE) functions in the catabolism of bioactive peptides. Established roles include degrading insulin and the amyloid beta peptide (Aβ), linking it to diabetes and Alzheimer's disease. IDE is primarily located in the cytosol, and a longstanding question is how it gains access to its peptide substrates.

Inositol phosphates and phosphoinositides activate insulin-degrading enzyme, while phosphoinositides also mediate binding to endosomes.

Insulin-degrading enzyme (IDE) hydrolyzes bioactive peptides, including insulin, amylin, and the amyloid β peptides. Polyanions activate IDE toward some substrates, yet an endogenous polyanion activator has not yet been identified. Here we report that inositol phosphates (InsPs) and phosphatdidylinositol phosphates (PtdInsPs) serve as activators of IDE.

An Extended Polyanion Activation Surface in Insulin Degrading Enzyme.

Insulin degrading enzyme (IDE) is believed to be the major enzyme that metabolizes insulin and has been implicated in the degradation of a number of other bioactive peptides, including amyloid beta peptide (Aβ), glucagon, amylin, and atrial natriuretic peptide. IDE is activated toward some substrates by both peptides and polyanions/anions, possibly representing an important control mechanism and a potential therapeutic target. A binding site for the polyanion ATP has previously been defined crystallographically, but mutagenesis studies suggest that other polyanion binding modes likely exist on the same extended surface that forms one wall of the substrate-binding chamber.

Obesity and diabetes cause cognitive dysfunction in the absence of accelerated β-amyloid deposition in a novel murine model of mixed or vascular dementia.

Mid-life obesity and type 2 diabetes mellitus (T2DM) confer a modest, increased risk for Alzheimer's disease (AD), though the underlying mechanisms are unknown. We have created a novel mouse model that recapitulates features of T2DM and AD by crossing morbidly obese and diabetic db/db mice with APPΔNL/ΔNLx PS1P264L/P264L knock-in mice. These mice (db/AD) retain many features of the parental lines (e.

Cysteine 904 is required for maximal insulin degrading enzyme activity and polyanion activation.

Cysteine residues in insulin degrading enzyme have been reported as non-critical for its activity. We found that converting the twelve cysteine residues in rat insulin degrading enzyme (IDE) to serines resulted in a cysteine-free form of the enzyme with reduced activity and decreased activation by polyanions. Mutation of each cysteine residue individually revealed cysteine 904 as the key residue required for maximal activity and polyanion activation, although other cysteines affect polyanion binding to a lesser extent.

Anion activation site of insulin-degrading enzyme.

Insulin-degrading enzyme (IDE) (insulysin) is a zinc metallopeptidase that metabolizes several bioactive peptides, including insulin and the amyloid β peptide. IDE is an unusual metallopeptidase in that it is allosterically activated by both small peptides and anions, such as ATP. Here, we report that the ATP-binding site is located on a portion of the substrate binding chamber wall arising largely from domain 4 of the four-domain IDE.

Identification of the allosteric regulatory site of insulysin.

Background: Insulin degrading enzyme (IDE) is responsible for the metabolism of insulin and plays a role in clearance of the Aβ peptide associated with Alzheimer's disease. Unlike most proteolytic enzymes, IDE, which consists of four structurally related domains and exists primarily as a dimer, exhibits allosteric kinetics, being activated by both small substrate peptides and polyphosphates such as ATP.

Principal Findings: The crystal structure of a catalytically compromised mutant of IDE has electron density for peptide ligands bound at the active site in domain 1 and a distal site in domain 2.

Mixed dimers of insulin-degrading enzyme reveal a cis activation mechanism.

Insulin-degrading enzyme (IDE) exists primarily as a dimer being unique among the zinc metalloproteases in that it exhibits allosteric kinetics with small synthetic peptide substrates. In addition the IDE reaction rate is increased by small peptides that bind to a distal site within the substrate binding site. We have generated mixed dimers of IDE in which one or both subunits contain mutations that affect activity.

A monomeric variant of insulin degrading enzyme (IDE) loses its regulatory properties.

Background: Insulin degrading enzyme (IDE) is a key enzyme in the metabolism of both insulin and amyloid beta peptides. IDE is unique in that it is subject to allosteric activation which is hypothesized to occur through an oligomeric structure.

Methodology/principal Findings: IDE is known to exist as an equilibrium mixture of monomers, dimers, and higher oligomers, with the dimer being the predominant form.

In vitro and in vivo degradation of Abeta peptide by peptidases coupled to erythrocytes.

It is generally believed that amyloid beta peptides (Abeta) are the key mediators of Alzheimer's disease. Therapeutic interventions have been directed toward impairing the synthesis or accelerating the clearance of Abeta. An equilibrium between blood and brain Abeta exists mediated by carriers that transport Abeta across the blood-brain barrier.

Proteolytic fragments of insulysin (IDE) retain substrate binding but lose allosteric regulation.

Treatment of an N-terminal-containing His6-tagged insulysin (His6-IDE) with proteinase K led to the initial cleavage of the His tag and linker region. This was followed by C-terminal cleavages resulting in intermediate fragments of approximately 95 and approximately 76 kDa and finally a relatively stable approximately 56 kDa fragment. The approximately 76 and approximately 56 kDa fragments exhibited a low level of catalytic activity but retained the ability to bind the substrate with a similar affinity as the native enzyme.

Susceptibility of amyloid beta peptide degrading enzymes to oxidative damage: a potential Alzheimer's disease spiral.

Insulysin (IDE) and neprilysin (NEP) were found to be inactivated by oxidation with hydrogen peroxide, an iron-ascorbate oxidation system, and by treatment with 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH). In each case reaction led to the introduction of protein carbonyl groups as judged by reaction with 2,4-dintrophenylhydrazine. IDE was inactivated by reaction with 4-hydroxy-2-nonenal (HNE) with the concomitant formation of protein adducts.

Insulysin: an allosteric enzyme as a target for Alzheimer's disease.

That the zinc metalloendopeptidase insulysin (insulin-degrading enzyme IDE) is a major b-amyloid (A(beta)) peptide-degrading enzyme in vivo is shown by the higher A(beta) peptide levels in the brain of an insulysin-deficient mouse. Insulysin was shown to initially cleave A(beta)1-40and A(beta)1-42 at His13-Gln14, His14-Gln15, and Phe19-Phe20. The insulysin-dependent cleavage of A(beta) prevents both the neurotoxic effects of the peptide as well as the ability of A(beta) to deposit onto synthetic amyloid plaques.

Mutation of active site residues of insulin-degrading enzyme alters allosteric interactions.

The active site glutamate (Glu(111)) and the active site histidine (His(112)) of insulin-degrading enzyme (IDE) were mutated. These mutant enzymes exhibit, in addition to a large decrease in catalytic activity, a change in the substrate-velocity response from a sigmoidal one seen with the native enzyme (Hill coefficient > 2), to a hyperbolic response. With 2-aminobenzoyl-GGFLRKHGQ-N-(2,4-dinitrophenyl)ethylenediamine as substrate, ATP and triphosphate increase the reaction rate of the wild type enzyme some 50-80-fold.

ATP effects on insulin-degrading enzyme are mediated primarily through its triphosphate moiety.

It has been reported previously that ATP inhibits the insulysin reaction (Camberos, M. C., Perez, A.

Substrate activation of insulin-degrading enzyme (insulysin). A potential target for drug development.

The rate of the insulin-degrading enzyme (IDE)-catalyzed hydrolysis of the fluorogenic substrate 2-aminobenzoyl-GGFLRKHGQ-ethylenediamine-2,4-dinitrophenyl is increased 2-7-fold by other peptide substrates but not by peptide non-substrates. This increased rate is attributed to a decrease in Km with little effect on Vmax. An approximately 2.