Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

A relatively simple protein solvent-accessible surface triangulation method for continuum electrostatics applications employing the boundary element method is presented. First, the protein is placed onto a three-dimensional lattice with a specified lattice spacing. To each lattice point, a box is assigned. Boxes located in the solvent region and in the interior of the protein are removed from the set. Improper connections between boxes and the possible existence of cavities in the interior of the protein which would destroy the proper connectivity of the triangulated surface are taken care of. The remaining set of boxes define the outer contour of the protein. Each free face exposed to the solvent of the remaining set of boxes is triangulated after the surface defined by the free faces has been smoothed to follow the shape of the macromolecule more accurately. The final step consists of a mapping of triangle vertices onto a set of surface points which define the solvent-accessible surface. Normal vectors at triangle vertices are obtained also from the free faces which define the orientation of the surface. The algorithm was tested for six molecules including four proteins; a dipeptide, a helical peptide consisting of 25 residues, calbindin, lysozyme, calmodulin and cutinase. For each molecule, total areas have been calculated and compared with the result computed from a dotted solvent-accessible surface. Since the boundary element method requires a low number of vertices and triangles to reduce the number of unknowns for reasons of efficiency, the number of triangles should not be too high. Nevertheless, credible results are obtained for the total area with relative errors not exceeding 12% for a large lattice spacing (0.30 nm) while close to zero for a smaller lattice spacing (down to 0.16 nm). The output of the triangulation computer program (written in C++) is rather simple so that it can be easily converted to any format acceptable for any molecular graphics programs.
 ...
PMID:A flexible triangulation method to describe the solvent-accessible surface of biopolymers. 974 71

We have studied the thermal stability of the triglyceride-hydrolyzing enzyme cutinase from F. solani pisi at pH values straddling the pI (pH 8.0). At the pI, increasing the protein concentration from 5 to 80 microM decreases the apparent melting temperature by 19 degrees C. This effect vanishes at pH values more than one unit away from pI. In contrast to additives such as detergents and osmolytes, the hydrophobic fluorophore 1,8-ANS completely and saturably suppresses this effect, restoring 70% of enzymatic activity upon cooling. ANS binds strongly to native cutinase as a noncompetitive inhibitor with up to 5 ANS per cutinase molecule. Only the first ANS molecule stabilizes cutinase; however, the last 4 ANS molecules decrease Tm by up to 7 degrees C. Similar pI-dependent aggregation and suppression by ANS is observed for T. lanuginosus lipase, but not for lysozyme or porcine alpha-amylase, suggesting that this behavior is most prevalent for proteins with affinity for hydrophobic substrates and consequent exposure of hydrophobic patches. Aggregation may be promoted by a fluctuating ensemble of native-like states associating via intermolecular beta-sheet rich structures unless blocked by ANS. Our data highlight the chaperone activity of small molecules with affinity for hydrophobic surfaces and their potential application as stabilizers at appropriate stoichiometries.
 ...
PMID:pH-dependent aggregation of cutinase is efficiently suppressed by 1,8-ANS. 1696 99

Aromatic amino acids play an important role in ultraviolet (UV)-induced photochemical reactions in proteins. In this work, we aim at gaining insight into the photochemical reactions induced by near-UV light excitation of aromatic residues that lead to breakage of disulfide bridges in our model enzyme, Fusarium solani pisi cutinase, a lipolytic enzyme. With this purpose, we acquired transient absorption data of cutinase, with supplemental experimental data on tryptophan (Trp) and lysozyme as reference molecules. We here report formation kinetics and lifetimes of transient chemical species created upon UV excitation of aromatic residues in proteins. Two proteins, lysozyme and cutinase, as well as the free amino acid Trp, were studied under acidic, neutral, and alkaline conditions. The shortest-lived species is assigned to solvated electrons (lifetimes of a few microseconds to nanoseconds), whereas the longer-lived species are assigned to aromatic neutral and ionic radicals, Trp triplet states, and radical ionic disulphide bridges. The pH-dependent lifetimes of each species are reported. Solvated electrons ejected from the side chain of free Trp residues and aromatic residues in proteins were observed 12 ns after excitation, reaching a maximum yield after approximately 40 ns. It is interesting to note that the formation kinetics of solvated electrons is not pH-dependent and is similar in the different samples. On the other hand, a clear increase of the solvated electron lifetime is observed with increasing pH. This observation is correlated with H3O+ being an electron scavenger. Prolonged UV illumination of cutinase leads to a larger concentration of solvated electrons and to greater absorption at 410 nm (assigned to disulphide electron adduct RSSR *-), with concomitant faster decay kinetics and near disappearance of the Trp* radical peak at 330 nm, indicating possible additional formation of TyrO* formed upon reaction of Trp* with Tyr residues. Prolonged UV illumination of cutinase also leads to a larger concentration of free thiol groups, known to originate from the dissociation of RSSR *-. Additional mechanisms that may lead to the near disappearance of Trp(*) are discussed. Our study provides insight into one key UV-light-induced reaction in cutinase, i.e., light-induced disruption of disulphide bridges mediated by the excitation of aromatic residues. Knowledge about the nature of the formed species and their lifetimes is important for the understanding of UV-induced reactions in humans that lead to light-induced diseases, e.g., skin cancer and cataract formation.
 ...
PMID:Flash photolysis of cutinase: identification and decay kinetics of transient intermediates formed upon UV excitation of aromatic residues. 1958 Jul 59

Protein stability assessment of seven model proteins in the presence of low molecular weight polyethyleneimine (PEI, MW 2000 Da) was performed. Thermodynamic stability, monitored by circular dichroism (CD) spectroscopy, showed that the polymer did not have a major effect on the melting temperature (T(m)) of the basic proteins - muscle lactate dehydrogenase (LDH), ribonuclease A, lysozyme and cutinase, while for the acidic ones - human growth hormone, human serum albumin and heart lactate dehydrogenase - there was a shift in T(m) towards lower temperatures. The secondary structures of the basic proteins were essentially the same, with none or a slight increase in the CD spectra, in presence of the polymer. In the case of the acidic proteins, the CD spectra were diminished mostly due to phase separation. Assuming a homogeneous distribution of the net charge on the protein surface a quantitative inverse relationship was established between surface charge density of the acidic proteins and the PEI(2000) concentration required for maximum flocculation. Despite lowering the thermal stability of acidic proteins, PEI(2000) was seen to protect heart LDH at an increasing oxidative stress.
 ...
PMID:Polyethyleneimine-protein interactions and implications on protein stability. 2041 30