2-Arachidonoylglycerol is a substrate for butyrylcholinesterase: A potential mechanism for extracellular endocannabinoid regulation

2-Arachidonoylglycerol (2-AG) is a component of the endocannabinoid receptor pathway and is primarily hydrolyzed by monoacylglycerol lipase (MAGL) in vivo. We found that the non-specific serine esterase, butyrylcholinesterase (BChE), can hydrolyze 2-AG with reasonable affinity and may present a new compensatory mechanism for endocannabinoid regulation. In vitro hydrolysis reactions of 2-AG with equine BChE were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) positive/negative electrospray ionization (ESI±) to measure the formation of arachidonic acid (AA) and the loss of 2-AG over time (min). The resulting Michaelis-Menten approximations reveal that BChE has affinity towards 2-AG in phosphate buffer at neutral pH (7.4). The calculated Vmax, Km and kcat were 12.1nmols(-1), 57.5μM, and 0.074s(-1), respectively, which produced a diffusion-controlled rate of association (kcat/Km) of 1.3×10(3)M(-1)s(-1). Human BChE 2-AG hydrolysis was measured by immunoprecipitating BChE from fresh plasma and monitoring 2-AG loss and AA formation over time. These findings show that BChE can hydrolyze 2-AG which may be evidence of a more specific role for BChE in endocannabinoid regulation.

Increased anandamide uptake by sensory neurons contributes to hyperalgesia in a model of cancer pain

Opioids do not effectively manage pain in many patients with advanced cancer. Because anandamide (AEA) activation of cannabinoid type-1 receptors (CB1R) on nociceptors reduces nociception, manipulation of AEA metabolism in the periphery may be an effective alternative or adjuvant therapy in the management of cancer pain. AEA is hydrolyzed by the intracellular enzyme fatty acid amide hydrolase (FAAH), and this enzyme activity contributes to uptake of AEA into neurons and to reduction of AEA available to activate CB1R. We used an in vitro preparation of adult murine dorsal root ganglion (DRG) neurons co-cultured with fibrosarcoma cells to investigate how tumors alter the uptake of AEA into neurons. Evidence that the uptake of [(3)H]AEA into dissociated DRG cells in the co-culture model mimicked the increase in uptake that occurred in DRG cells from tumor-bearing mice supported the utility of the in vitro model to study AEA uptake. Results with the fluorescent AEA analog CAY10455 confirmed that an increase in uptake in the co-culture model occurred in neurons. One factor that contributed to the increase in [(3)H]AEA uptake was an increase in total cellular cholesterol in the cancer condition. Treatment with the FAAH inhibitor URB597 reduced CAY10455 uptake in the co-culture model to the level observed in DRG neurons maintained in the control condition (i.e., in the absence of fibrosarcoma cells), and this effect was paralleled by OMDM-1, an inhibitor of AEA uptake, at a concentration that had no effect on FAAH activity. Maximally effective concentrations of the two drugs together produced a greater reduction than was observed with each drug alone. Treatment with BMS309403, which competes for AEA binding to fatty acid binding protein-5, mimicked the effect of OMDM-1 in vitro. Local injection of OMDM-1 reduced hyperalgesia in vivo in mice with unilateral tumors in and around the calcaneous bone. Intraplantar injection of OMDM-1 (5μg) into the tumor-bearing paw reduced mechanical hyperalgesia through a CB1R-dependent mechanism and also reduced a spontaneous nocifensive behavior. The same dose reduced withdrawal responses evoked by suprathreshold mechanical stimuli in naive mice. These data support the conclusion that OMDM-1 inhibits AEA uptake by a mechanism that is independent of inhibition of FAAH and provide a rationale for the development of peripherally restricted drugs that decrease AEA uptake for the management of cancer pain.

Thermal stability of rhodopsin and progression of retinitis pigmentosa: comparison of S186W and D190N rhodopsin mutants

Over 100 point mutations in the rhodopsin gene have been associated with retinitis pigmentosa (RP), a family of inherited visual disorders. Among these, we focused on characterizing the S186W mutation. We compared the thermal properties of the S186W mutant with another RP-causing mutant, D190N, and with WT rhodopsin. To assess thermal stability, we measured the rate of two thermal reactions contributing to the thermal decay of rhodopsin as follows: thermal isomerization of 11-cis-retinal and hydrolysis of the protonated Schiff base linkage between the 11-cis-retinal chromophore and opsin protein. We used UV-visible spectroscopy and HPLC to examine the kinetics of these reactions at 37 and 55 °C for WT and mutant rhodopsin purified from HEK293 cells. Compared with WT rhodopsin and the D190N mutant, the S186W mutation dramatically increases the rates of both thermal isomerization and dark state hydrolysis of the Schiff base by 1-2 orders of magnitude. The results suggest that the S186W mutant thermally destabilizes rhodopsin by disrupting a hydrogen bond network at the receptor's active site. The decrease in the thermal stability of dark state rhodopsin is likely to be associated with higher levels of dark noise that undermine the sensitivity of rhodopsin, potentially accounting for night blindness in the early stages of RP. Further studies of the thermal stability of additional pathogenic rhodopsin mutations in conjunction with clinical studies are expected to provide insight into the molecular mechanism of RP and test the correlation between rhodopsin's thermal stability and RP progression in patients.

Molecular and practical aspects of the enzymatic properties of human serum albumin and of albumin-ligand complexes

BACKGROUND

Human serum albumin and some of its ligand complexes possess enzymatic properties which are useful both in vivo and in vitro.

SCOPE OF REVIEW

This review summarizes present knowledge about molecular aspects, practical applications and potentials of these properties.

MAJOR CONCLUSIONS

The most pronounced activities of the protein are different types of hydrolysis. Key examples are esterase-like activities involving Tyr411 or Lys199 and the thioesterase activity of Cys34. In the first case, hydrolysis involves water and both products are released, whereas in the latter cases one of the products is set free, and the other stays covalently bound to the protein. However, the modified Cys34 can be converted back to its reduced form by another compound/enzymatic system. Among the other activities are glucuronidase, phosphatase and amidase as well as isomerase and dehydration properties. The protein has great impact on the metabolism of, for example, eicosanoids and xenobiotics. Albumin with a metal ion-containing complex is capable of facilitating reactions involving reactive oxygen and nitrogen species.

GENERAL SIGNIFICANCE

Albumin is useful in detoxification reactions, for activating prodrugs, and for binding and activating drug conjugates. The protein can be used to construct smart nanotubes with enzymatic properties useful for biomedical applications. Binding of organic compounds with a metal ion often results in metalloenzymes or can be used for nanoparticle formation. Because any compound acting as cofactor and/or the protein can be modified, enzymes can be constructed which are not naturally found and therefore can increase, often stereospecifically, the number of catalytic reactions. This article is part of a Special Issue entitled Serum Albumin.

Promotion of the lipase-catalyzed hydrolysis of conjugated linoleic acid l-menthyl ester by addition of an organic solvent

Conjugated linoleic acid l-menthyl ester was hydrolyzed in water by the lipase from Candida rugosa with the addition of an organic solvent. The degree of hydrolysis (yield) greatly improved when a tertiary alcohol, such as t-butyl alcohol, was added. However, the addition of a less polar solvent, such as hexane, decreased the degree of hydrolysis, and some water-miscible solvents, such as acetone, caused inactivation of the lipase. With the addition of t-butyl alcohol, the reaction mixture formed a one- or two-phase system, and the mixing ratio of substrates and t-butyl alcohol determined the number of phases. Although the degree of hydrolysis at 10 d was higher in the one-phase system, the initial reaction rate was generally lower. Meanwhile, the reaction was much faster in the two-phase system while maintaining a moderate degree of hydrolysis.

Preparation of Carboxylato-Coordinated Titanium Alkoxides from Carboxylic Anhydrides: Alkoxido Group Transfer from Metal Atom to Carbonyl Group

Reaction of titanium(IV) isopropoxide, Ti(OiPr)₄, with an equimolar amount of phthalic anhydride resulted in the transfer of an isopropoxido group from the metal atom to one carbonyl group of the anhydride and coordination of the thus formed monoester to the titanium atom. One monoester ligand in Ti₂(OiPr)₆(μ₂-OOC-C₆H₄-COOiPr)(η¹-OOC-C₆H₄-COOiPr)(iPrOH) is bridging and the other is η¹-coordinated. When the reaction is performed in the presence of 1 mol-equiv. of acetic acid, the oxido cluster Ti₆(μ₃-O)₆(OiPr)₆(μ₂-OOC-C₆H₄-COOiPr)₆ was instead obtained. The μ₃-oxygen groups in the latter compound are due to esterification of acetic acid by the cleaved isopropyl alcohol.

Alkali pretreated of wheat straw and its enzymatic hydrolysis

The efficiency of enzymatic hydrolysis of cellulose can be improved by various pretreatments of the substrate. In order to increase the efficiency of enzymatic saccharification of the wheat straw, we determined the effect of different pretreatments on the physical structure, chemical components and enzymatic saccharification of wheat straw. Our results showed that combination of grinding and sodium hydroxide (NaOH) treatment had high effect on the enzymatic hydrolysis of wheat straws. The optimal pretreatment condition was to grind the wheat straws into the sizes of 120 meshes followed by treatment with 1.0% NaOH for 1.5 h (121°C/15psi). Under this condition, the cellulose content of wheat straw was increased by 44.52%, while the content of hemicellulose and lignin was decreased by 44.15% and 42.52%, respectively. Scanning Electronic Microscopy and infrared spectrum analyses showed that significant changes occurred in the structure of wheat straws after pretreatment, which is favorable for the hydrolysis and saccharification. Cellulase produced by Penicillium waksmanii F10–2 was used to hydrolyze the pretreated wheat straw and the optimal condition was determined to be 30 h of enzymatic reaction under the temperature of 55°C, pH 5.5 and substrate concentration of 3%.

Effect of various process treatment conditions on the allyl isothiocyanate extraction rate from mustard meal

Allyl isothiocyanate (AITC), which has the potential to be used as flavoring, antibacterial, antifungal, antifermentative and antibrowning agent in food industry, was extracted from the pretreated MM by distillation technique. The mustard meal was analyzed for the proximate composition and the metals Fe, Mg and Zn. At the optimum pretreatment conditions of temperature 60 °C, time 120 min and pH 4.5, the effect of fractional distillation, mesh size and different additives was studied. Considerable effect of mesh size was observed, as the mesh size was decreased from 1,690 to 400 μm, the allyl isothiocyanate content was increased from 99.15 to 337.11 mg/100 ml. Addition of magnesium chloride (0.05 g/l to 0.2 g/l) and L-ascorbic acid (1 g/l to 5 g/l) increased allyl isothiocyanate from 257.79 to 317.28 mg/100 ml and 316.77 to 396.60 mg/100 ml respectively whereas the addition of the magnesium chloride and L-ascorbic acid in combination did not affect the AITC extraction rate as compare to their addition in single effect.

Iron binding capacity of dephytinised soy protein isolate hydrolysate as influenced by the degree of hydrolysis and enzyme type

Soy protein is increasingly used in extended meat products and dairy type products due to the presence of high quality proteins with excellent functional properties. However, it has been shown to inhibit iron bioavailability because of phytic acid present in the protein. This present study investigated the effects of dephytinise from soy protein isolate (SPI) on iron binding capacity and degree of hydrolysis. Also the effects of enzyme type and degree of hydrolysis on iron binding capacity were studied. It was demonstrated that phytase and anion exchange resin could remove effectively the phytate from SPI. The dephytinise would decrease the degree of hydrolysis of SPI. The enzyme type and degree of hydrolysis influenced significantly the iron binding capacity of the hydrolysate. Flavourzyme might be the best choice for producing peptides with iron binding capacity from SPI and middle degree of hydrolysis would be benefitable to this process.

Thermal degradation of groundnut oil during continuous and intermittent frying

The quality of refined groundnut oil, as affected by frying Poori, was assessed with respect to two types of frying operations viz., continuous frying and intermittent frying. Continuous frying was carried out consistently for 8 h, whereas intermittent frying was performed for 2 h everyday for 4 days for a total of 8 frying hours. The purpose of the study was to compare the level of deterioration that occurred during the two operations. Among the parameters studied, peroxide value (11.3 ± 0.26 meqO2/kg), anisidine value (172.4 ± 2.71), diene value (1.57 ± 0.095), oxidized fatty acid (2.6 ± 0.17%) and viscosity (103.8 ± 2.5 mPa s(-1)), were found to be higher after 8 h due to intermittent frying. The corresponding values 4.9 ± 0.15, 133.3 ± 0.49, 0.811 ± 0.04, 0.38 ± 0.023 and 81.8 ± 2.02 were observed in continuous frying. Parameters such as iodine value, unsaturated fatty acids, saponification value and smoke point decreased significantly (P < 0.5) due to intermittent frying. Results showed that intermittent frying caused more quality degradation to GNO than continuous frying.

Ultrasound-assisted hydrolysis and gas chromatography-mass spectrometric determination of phenolic compounds in cranberry products

An ultrasound-assisted hydrolysis and gas chromatography-mass spectrometric (GC-MS) method has been developed for determination of phenolics in cranberry products. Prior to GC-MS separation and characterisation, the phenolics in samples were hydrolysed by hydrochloric acid with ultrasound-assistance, extracted with ethyl acetate, and derivatised with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)+1% trimethylchlorosilane (TMCS) reagents. The application of ultrasonication significantly accelerated the acidic hydrolysation of the conjugated phenolics. A baseline separation of the 20 phenolics and internal standard was achieved in 25min. Standard calibration curves were linear over the concentration range of 0.0-50μg/mL and detection limits were 0.06-0.70μg/mL. Twenty phenolics were identified in cranberry samples and all of them occurred mainly in conjugated forms. Of those, the benzoic acid, quercetin, and myricetin were most abundant phenolics. The total phenolics were 12.4mg/g in cranberry fruits, 9.1mg/mL in 100% cranberry juice, and 11.1mg/g in cranberry sauces, respectively.

Hydrolysis of green tea residue protein using proteolytic enzyme derived from Aspergillus oryzae

Free amino acids are important chemical components which impact the taste of green tea infusion. The hydrolysis of water-insoluble protein in the green tea residue helps to increase the contents of free amino acids components except theanine. Studies indicate that the hydrolysis of the tea protein could be restricted due to interaction of polyphenols with protein. The experiment indicates that the hydrolysis of tea protein by protease is the main trend when the polyphenols concentration is lower than 5 mg ml(-1), however, the proteins (including tea protein and protease) would interact with polyphenoles instead of hydrolysis when the concentration of polyphenols is higher than 5 mg ml(-1). The hydrolysis of tea protein is absolutely restrained when concentration comes to 10 mg ml(-1).

Study of hydrolytic kinetics of the hexachlorostannate anion by two-dimensional 119 Sn exchange spectroscopy

Two-dimensional ¹¹⁹ Sn exchange spectroscopy was applied to study the hydrolytic kinetics of the hexachloro-stannate anion, SnCl₆ ^2- . Two ¹¹⁹ Sn exchange spectra for SnCl₄ · 5H₂ O solutions with various HCl concentrations are presented. Magnetization exchanges, which are related to the hydrolysis processes, occur in the SnCl₆ ^2- hydrolysis series. The exchange rate constants, the hydrolysis rate constants and the hydrolysis equilibrium constants were evaluated.