Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.8.1.4 (diaphorase)
 2,754 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The dihydrolipoyl transacetylase (E2) component contains a COOH-terminal inner domain (E2I) and an extended NH2-terminal structure, which is composed of two lipoyl domains (the fragment containing both is designated as E2L) and a subunit-binding domain (E2B). The four domains are connected by hinge regions. A subcomplex, composed of an oligomer of E2 subunits, protein X (which also has an NH2-terminal lipoyl domain), and the [pyruvate dehydrogenase]-kinase catalytic and basic subunits (Kc and Kb, respectively) (i.e. E2.X.KcKb subcomplex), was treated with Clostridium histolyticum collagenase. E2 subunits were selectively cleaved at the NH2-terminal end of the E2B domain, releasing the E2L fragment. Complete release of E2 subunits also released the kinase subunits, indicating that the kinase is bound to the E2L portion of E2. The residual inner core subcomplex (designated E2IB.X) has a strong tendency to aggregate, but this can be reversed with heparin (1 mg/ml). The E2IB.X subcomplex binds the pyruvate dehydrogenase (E1) and dihydrolipoyl dehydrogenase (E3) components. The E1 component, which binds to the E2B domain, blocked collagenase cleavage of E2. We evaluated the capacity of the collagenase-treated E2.X.KcKb subcomplex, from which different portions of the E2L domains were removed, to support (in combination with excess levels of the E1 and E3 components) the overall reaction of the complex. Loss of activity occurred only after more than half of the E2L domains were removed. This delay is in sharp contrast to the effect of selective removal of the lipoyl domain of protein X, which leads to an immediate decrease in activity (Gopalakrishnan, S., Rahmatullah, M., Radke, G.-A., Powers-Greenwood, S. L., and Roche, T. E. (1989) Biochem. Biophys. Res. Commun. 160, 715-721). These results suggest that multiple lipoyl domains of the E2 component service the rate-limiting E1 component. After all the E2L domains were removed and the E2IB.X subcomplex was separated from free E2L, 10% activity was retained in the overall reaction. Thus, the lipoyl domain of protein X supported the overall reaction of the complex.
 ...
PMID:Changes in the core of the mammalian-pyruvate dehydrogenase complex upon selective removal of the lipoyl domain from the transacetylase component but not from the protein X component. 216 19

Mammalian pyruvate dehydrogenase complex (PDC) contains a subunit, protein X, which mediates high-affinity binding of dihydrolipoamide dehydrogenase (E3)to the dihydrolipoamide acetyltransferase (E2) core. Precise stoichiometric determinations on bovine heart PDC, by means of two approaches, indicate the presence of 12 mol protein X/mol PDC and 60 mol E2/mol PDC. Studies of the organisation of collagenase-modified PDC by means of covalent cross-linking of N,N'-1,2-phenylenedimaleimide to lipoamide thiols on protein X, reveal that the main cross-linked products have Mr values corresponding to homodimers of protein X. However, significant formation of higher-Mr aggregates indicates that lipoyl domains of protein X can form an interacting network independent of E2 lipoyl domains. These data suggest that either 12 interacting X monomers or 6 interacting X dimers are involved in the binding of six E3 homodimers to the E2/X core. The presence of 60 E2 subunits/complex also supports proposals for a non-integrated external position of protein X. Collagenase-treated PDC possesses residual activity (15 %), indicating that protein-X-linked lipoamide groups can substitute for the lipoyl domains of E2 in overall complex catalysis. Protein-X-mediated diacetylation of dihydrolipoamide moieties is also performed by the modified complex which raises the possibility of a unique catalytic function for protein X.
 ...
PMID:Stoichiometry, organisation and catalytic function of protein X of the pyruvate dehydrogenase complex from bovine heart. 861 88

X-ray diffraction is used to study the binding of xenon and krypton to a variety of crystallised proteins: porcine pancreatic elastase; subtilisin Carlsberg from Bacillus licheniformis; cutinase from Fusarium solani; collagenase from Hypoderma lineatum; hen egg lysozyme, the lipoamide dehydrogenase domain from the outer membrane protein P64k from Neisseria meningitidis; urate-oxidase from Aspergillus flavus, mosquitocidal delta-endotoxin CytB from Bacillus thuringiensis and the ligand-binding domain of the human nuclear retinoid-X receptor RXR-alpha. Under gas pressures ranging from 8 to 20 bar, xenon is able to bind to discrete sites in hydrophobic cavities, ligand and substrate binding pockets, and into the pore of channel-like structures. These xenon complexes can be used to map hydrophobic sites in proteins, or as heavy-atom derivatives in the isomorphous replacement method of structure determination.
 ...
PMID:Exploring hydrophobic sites in proteins with xenon or krypton. 944 41

Paeonia suffruticosa Andr. (PS) has been used in traditional Chinese medicine for a long time. However, there are no studies that investigate the preventive effects of PS on ultraviolet B (UVB)-induced photoaging. In this study, paeonol (PA) was detected the main compound in PS root. In vitro, PS and PA significantly inhibited UVB-induced phosphorylation of mitogen-activated protein kinase and activator protein 1 in keratinocytes, which consequently led to degradation of procollagen type I. On the other hand, PS and PA increased NAD(P)H:quinone oxidoreductase 1 and heme oxygenase-1 expression, confirmed by greater nuclear accumulation of nuclear factor E2-releated factor 2 (Nrf2). Furthermore, this study proved that the endogenous antioxidant system Nrf2/antioxidant response element was regulated by dihydrolipoamide dehydrogenase, a tricarboxylic acid (TCA) cycle-associated protein whose level was decreased after UVB exposure. PS and PA promoted the production of dihydrolipoamide dehydrogenase, as well as the activation of Nrf2 and antioxidant response element, resulting in preventing procollagen type I ruined caused by UVB. In vivo, topical application of PS and PA attenuated UVB-induced matrix metalloproteinase-1 production and promoted procollagen type I in hairless mice. These results suggested PA a promising botanical in protecting skin from UVB-induced photoaging.
 ...
PMID:Paeonol extracted from Paeonia suffruticosa Andr. ameliorated UVB-induced skin photoaging via DLD/Nrf2/ARE and MAPK/AP-1 pathway. 2974 77