1,720,982 research outputs found
Modulazione dell'attività catalitica di lipasi: uso di solventi ed anticorpi monoclonali
No full textFrom organic solvents to supercritical fluids and ionic liquids: the role of the medium in the applied biocatalysis
No full textWe have been working in different applications of lipases from different sources, wild and mutated, with different classes of organic solvents and different model substrates, trying to establish some correlations between physico-chemical characteristics of the solvents and structural aspects of the substrate. More recently, room-temperature ionic liquids have been also employed as media for biocatalysed reactions. Besides potential environmental benefits, ionic liquids permit enzyme-catalysed reactions in a solvent polarity range that was previously inaccessible, offering major advantages with polar substrates
Chemoenzymatic transformation in the pharmaceutical industry: lipase catalyzed resolution of alpha-aryl aceitc acids
No full textSome results and some general observations on parameters which can modulate and enhance the Candida rugosa lipase reactivity and selectivity in hydrolysis and synthesis reactions have been reported
High yield and optical purity of biocatalysed acylation of trans-2-phenylcyclohexanol with Candida rugosa lipase in non conventional media
No full textCandida rugosa lipase (CRL) shows high enantioselectivity toward (1R,2S)-(−)-trans-2-phenyl-1-cyclohexanol enantiomer in acetylation reaction employing vinyl acetate as acyl donor. Attempts to improve reaction yields have pointed out that supercritical CO2 is the best reaction medium in the studied biocatalytic process. In these conditions an immobilised lipase from Candida rugosa is able to quantitatively resolve racemate with e.e.p 100%
An approach to the interpretation of lipase mechanism in transesterification reaction employing an ordered Bi-Bi mechanism
No full textChromatographic separation of different lipases in human pre- and post-heparin plasma
No full textHuman plasma was applied to small heparin-sepharose solumn and the different lipases were eluted and separated with NaCl gradient. Then the plasma was submitted to chromatography. Different hepatic lipase and lipoprotein lipase in post-heparin plasma were detected. This methodology can be helpfully employed in monitoring the hepatic lipase increasing in plamsa during hepatic disease
Effect of pressure on enzymatic reactions in supercritical fluids
No full textThe use of supercritical fluids as reaction media for biocatalysed reactions can be considered a useful tool to modulate enzymatic performance modifying solvent physico-chemical properties. We studied the performance of Pseudomonas cepacea lipase in the acylation of (+/-)-1-phenylethanol with vinyl acetate in supercritical and near-critical CO2. We examined the effect of pressure on reaction rates and enzyme selectivity and in terms of catalytic efficiency of lipase estimating the activation volume for the process. The study of the kinetic mechanism of reaction suggested a Ping-Pong Bi-Bi mechanism with inhibition by vinyl acetate
Latex lipase of Euphorbia characias L.: An aspecific acylhydrolase with several isoforms
No full textThe objective of the present work was to contribute to the understanding of the physiological role of latex lipolytic activity in Euphorbia characias. To this end, the acid and basic lipolytic activity of E. characias latex, as well as the substrate specificity on various triacylglycerols, were measured during the plant's vegetative and reproductive stages. Both activities appeared to increase during the reproductive stage and to peak at the beginning of the vegetative stage, when new leaves and branches are formed. For the first time, the phospholipolytic and esterase activity of E. characias latex is also reported. An extraction method in aqueous medium with the zwitterionic detergent CHAPS was successfully used to extract lipolytic activity from latex. Extraction permitted the selective recovery of a single protein spot, with a molecular weight of 37 kDa, and presumably made of several acid isoforms which retained both lipolytic and phospholipolytic activity. The biochemical results suggest that lipolytic and phospholipolytic activity could depend on a single hydrolytic enzyme with several isoforms, equally expressed throughout the biological cycle of the plant. On the basis of the obtained results, we hypothesise that the E. characias latex lipase should be considered as an aspecific acylhydrolase with a combined lipase/phospholipase A activity
The role of reaction medium in lipase-catalyzed esterifications and transesterifications
No full textThe nature of the reaction medium (different organic solvents and supercritical fluids) markedly influenced the microbial lipase activity in esterification and transesterification reactions employing as substrates natural and synthetic compounds in terms of reaction rates and lipase enantioselectivity. The experimental data obtained show that while there are no substantial correlations between enantioselectivity and some physicochemical characteristics of the solvent as hydrophobicity and dielectric constant, the solvent polarity and hydrophobicity is able to modulate greatly lipase activity. The possible effects of the solvent characteristics on the catalytic performance of the enzymes are discussed and a rationale is proposed to explain the results obtained
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