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:1.10.3.2 (laccase)
4,656 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The optimum pH for ceruloplasmin as polyphenol oxidase (EC 1.10.3.2) activity was determined in human serum (pH 5.4) and the serum of conventional laboratory animals--the rat (pH 5.2), mouse (pH 5.2), hamster (pH 5.3), guinea pig (pH 5.4), multimammate mouse (pH 5.2) and rabbit (pH 5.4). Determined at the optimum pH in 0.1M acetate buffer polyphenol oxidase activity fell in the sequence: rat--man--rabbit--mouse--multimammate mouse--hamster--guinea pig. Ceruloplasmin polyphenol oxidase activity was inhibited by 0.1M phosphate buffer in the mouse, rat and multimammate mouse, but not in the other species. It was inhibited by 0.05M citrate and 0.1M phthalate buffer in all the species tested.
...
PMID:Serum polyphenol oxidase activity (ceruloplasmin) in conventional laboratory animals and man. 2 13

A mechanistic study of the anation of type 2 Cu(II) in fully oxidized laccase by azide and thiocyanate ions (X-) is reported. The rate data support a mechanism involving rapid formation of an outer-sphere complex (laccase . X-) followed by rate-limiting dissociative interchange to give the inner-sphere complex (laccase-X-) product: (formula; see text) Rate parameters for the laccase-azide reaction are k'2 = 1.25 X 10(-1) s-1 and k'-2 = 1.50 X 10(-2) s-1; those for the laccase-thiocyanate reaction are k'2 = 2.0 X 10(-2) s-1 and k'-2 = 1.1 X 10(-2) s-1 (25 degrees C, pH 6.1 phosphate buffer, I = 0.5 M). Although the rate law for anation of type 2 Cu(II) by N3- in 2-(N-morpholino)ethanesulfonic acid (Mes) or acetate medium (kobsd = k3 + k4[N3-]) differs from that observed in phosphate buffer, the data may still be accounted for in terms of the above mechanism, with Kos[N3-] much less than 1 [in Mes, k3 = 2.2 X 10(-2) s-1 and k4 = 3.3 X 10(-1) M-1 s-1; in acetate, k3 = 2.1 X 10(-2) s-1 and k4 = 3.4 X 10(-1) M-1 s-1 (25 degrees C, pH 6.0, I = 0.25 M)]. The equilibrium and spectroscopic characteristics of the laccase type 2 Cu(II)-N3- complex are compared with those of low molecular weight copper(II)-azide species, and the factors responsible for the very low substitutional reactivity of the type 2 cupric ion are discussed.
...
PMID:Anation of laccase type 2 copper by azide and thiocyanate ions. 712 48

We have improved a method for the removal of the type 2 copper from tree laccase under anaerobic reducing conditions and developed a mechanistic model. We identify two key steps in the reaction: (i) dissociation of copper(I) catalyzed by trace levels of cyanide in a weakly acidic medium and (ii) sequestration of the released metal by an appropriate chelator such as 2,9-dimethyl-1,10-phenanthroline. We maintain a steady-state concentration of cyanide in a pH 5.5 acetate buffer under a constantly exchanging nitrogen atmosphere by introducing a cyanometalate ion as a cofactor or by continuously injecting the ion into the protein solution. The type 2-depleted product is identical to previous preparations as regards its spectral properties, activity level and ability to recombine with copper(I). The mechanistic insights appear to be quite general and should form the basis for the development of methods for removing the type 2 copper from other related systems.
...
PMID:The role of cyanide in the removal of type 2 copper from laccase. 762 34

Effects of medium viscosity on kinetic parameters of poly(U) hydrolysis catalyzed by RNase from Bac. intermedius 7P (binase) were studied in solutions of sucrose (4-50 wt. %) and glycerol (35-62 wt. %) in Tris--sodium acetate buffer (pH 7.5) at 25 degreesC. The rate constant of reaction kcat was practically unchanged over a wide range of viscosities (1-15 cP for sucrose and 2.5-3 cP for glycerol). In glycerol solutions, kcat slightly increased with viscosity increase from 4 to 10 cP. Addition of NaCl to the buffer medium resulted in an inhibitory effect of Na+ on kcat, prevented by 50% sucrose or 60% glycerol. It is concluded that binase-catalyzed poly(U) cleavage occurs through a "tense"-substrate mechanism, similarly to reactions catalyzed by alpha-chymotrypsin, trypsin, and laccase.
...
PMID:Effects of medium viscosity on kinetics of the enzymatic reaction catalyzed by bacterial RNase 986 66

Blue laccase from Coriolus versicolor and blue and yellow laccases from Panus tigrinus were isolated, purified and studied in acetate buffer solutions, with and without addition of various amounts of ethanol, using syringaldazine and 2,6-dimethoxyphenol as substrates. Effect of ethanol on blue laccases could be successfully described using the mixed inhibition model, over the range of 0-2.5 M ethanol concentrations. Yellow laccase from P. tigrinus behaves differently, which may be explained by the presence of some extra molecules in its structure, which possibly stabilize the enzyme and might be exchanged in ethanol solutions.
...
PMID:Effect of ethanol on enzymatic activity of fungal laccases. 1084 Dec 75

The ascomycete, Botryosphaeria sp, produced two extracellular constitutive laccases (PPO-I and PPO-II) active toward the substrates: 2, 2(1)-azino-bis(3-ethyl-benzthiazoline-6-sulfonic acid) [ABTS], and 2,6-dimethoxyphenol (DMP), respectively. The production of both laccases increased when the fungal isolate was grown in the presence of veratryl alcohol, and resulted in optimal laccase production (100- and 25- fold, respectively) at 40 mM. The effect of aeration on growth and laccase production was studied in baffled flasks, and showed that aeration of the cultures increased the production of both enzymes 4-5 fold in the presence of veratryl alcohol. Both laccases were susceptible to inhibition by azide, acetate and chloride anions. Veratryl alcohol inhibited the laccase-catalyzed polymerization of DMP. Growing cultures of Botryosphaeria sp. produced an exopolysaccharide of the beta-glucan type whose synthesis was depressed when grown in the presence of veratryl alcohol.
...
PMID:The effects of aeration and veratryl alcohol on the production of two laccases by the ascomycete Botryosphaeria sp. 1111 1

Laccase-catalyzed oxidative polymerization of 1-naphthol was carried out in a closed system containing acetone and sodium acetate buffer. The effects of initial 1-naphthol and dissolved oxygen concentrations on the initial reaction rate were investigated. A multiplicative mathematical model, using a function of 1-naphthol and dissolved oxygen concentrations, was developed for enzymatic polymerization and the corresponding biokinetic parameters have been evaluated for the first time. The activation energy and reaction rate constant of the laccase-catalyzed 1-naphthol polymerization were calculated as 57 kJ/mol and 311 l/s, respectively. The activation energy calculated was in the typical range of 30-60 kJ/mol and rate constant was of the order of magnitude of previously reported values for laccase-catalyzed reactions with different monomers.
...
PMID:Reaction kinetics for laccase-catalyzed polymerization of 1-naphthol. 1155 98

Poly(catechol) was synthesized in batch runs with laccase from Trametes versicolor (ATCC 200801). The polymerization reaction was conducted in a closed, temperature controlled system containing acetone and sodium acetate buffer for pH control. The effects of the solvent mixture, monomer (catechol), enzyme, medium pH and temperature on the polymerization rate were investigated with respect to initial reaction conditions and depletion rate of dissolved oxygen in the medium. Maximum initial reaction rate was attained with 10% (v/v) acetone-sodium acetate buffer at pH 5.0, 25 degrees C, 0.02 U/ml enzyme and 250 mg/l initial catechol and 10 mg/l dissolved oxygen. A general saturation enzyme kinetics response was observed for catechol substrate. Temperature rise supported the rate increase up to 45 degrees C, after which the rate tended to be stable due to a drop in dissolved oxygen concentration as well as enzyme instability.
...
PMID:Reaction conditions for laccase catalyzed polymerization of catechol. 1250 58

Substituted benzyl alcohol was oxidized enzymatically with a laccase-mediator system and the products were investigated as a function of time by nanoelectrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (nanoESI-FTICRMS). With Trametes versicolor laccase (TVL), the mediator, 2,2',6,6'-tetramethylpiperidine-N-oxyl radical (TEMPO), undergoes oxidation and forms oxoammonium ion. Oxidized TEMPO oxidizes the alcohol and is simultaneously reduced to the N-OH form. The laccase then restores TEMPO back to the normal radical form and the oxidation cycle starts again. The role of TEMPO and the structures of its oxidized and reduced forms in the enzymatic oxidation process were clarified in collision-induced dissociation experiments and gas-phase hydrogen/deuterium (H/D) exchange reactions. The amounts of enzyme and mediator were significant for product formation: with greater amounts overoxidation products, the corresponding benzoic acid and benzonitrile were formed. Smaller amounts of laccase and mediator generated benzaldehyde in high yield. The reaction pathway for benzonitrile formation is discussed and it is suggested to start from benzaldehyde and the ammonia in the ammonium acetate buffer.
...
PMID:Laccase-catalyzed mediated oxidation of benzyl alcohol: the role of TEMPO and formation of products including benzonitrile studied by nanoelectrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. 1546 36

A comparative study on solid substrate fermentation (SSF) of sago 'hampas', oil palm frond parenchyma tissue (OPFPt) and rubberwood sawdust with Pycnoporus sanguineus for laccase production was carried out. Optimal mycelial growth of Pyc. sanguineus was observed on all the substrates studied over a 21 days time-course fermentation. Laccase productivity was highest during degradation of sago 'hampas' and OPFPt and a range from 7.5 to 7.6 U/g substrate on the 11th day of fermentation compared to degradation of rubberwood sawdust with a maximum laccase productivity of 5.7 U/g substrate on day 11 of SSF. Further optimization of laccase production was done by varying the inoculum age, density and nitrogen supplementation. SSF of OPFPt by Pyc. sanguineus gave maximum productivity of laccase of 46.5 U/g substrate on day 6 of fermentation with a 30% (w/w) of 4 weeks old inoculum and 0.92% nitrogen in the form of urea supplemented in the substrate. The extraction of laccase was also optimized in this study. Recovery of laccase was fourfold higher at 30.6 U/g substrate on day 10 of SSF using unadjusted tap water at pH 8.0 as extraction medium at 25+/-2 degrees C compared to laccase recovery of 7.46 U/g substrate using sodium acetate buffer at pH 4.8 at 4 degrees C. Further optimization showed that laccase recovery was increased by 50% with a value of 46.5 U/g substrate on day 10 of SSF when the extraction medium was tap water adjusted to pH 5.0 at 25+/-2 degrees C.
...
PMID:Productivity of laccase in solid substrate fermentation of selected agro-residues by Pycnoporus sanguineus. 1596 61


1 2 3 4 5 Next >>

---