Analysis of conformational states of Candida rugosa lipase in solution: implications for mechanism of interfacial activation and separation of open and closed forms

Magnetic cross-linked enzyme aggregate based on ionic liquid modification as a novel immobilized biocatalyst for phytosterol esterification

Novel immobilized enzyme CRL-FIL-CLEAs@Fe3O4 with enhanced activities and stabilities was successfully prepared by a cross-linked lipase aggregate method for phytosterol esterification.

Immobilisation of Candida rugosa lipase on a highly hydrophobic support: A stable immobilised lipase suitable for non-aqueous synthesis

Lipase from Candida rugosa (CrL) was immobilised on highly hydrophobic, octadecyl methacrylate resin (Lifetech™ ECR8806M) via interfacial adsorption. The aim was to produce a stable biocatalyst suitable for use in a range of lipid-modifying reactions. Immobilisation was carried out in 10 mM phosphate buffer (pH 6.0) over 24 h at 21 °C. High protein binding of 58.7 ± 4.9 mg/g dry support accounted for ∼53 % of the applied protein. The activity recovery against tributyrin was 74.0 ± 1.1 %. The specific activity of immobilised CrL against tributyrin was considerably higher than that of Novozym® 435, at 1.79 ± 0.05 and 1.08 ± 0.04 U/mg bound protein, respectively. Incubation with high concentrations (10 % w/v) of both Triton X-100 and SDS resulted in only a small reduction in immobilised lipase activity. Solvent-free synthesis of glycerides by the FFA-saturated immobilised CrL was successful over 6 reaction cycles, with no apparent loss of activity.

Monobody-Mediated Alteration of Lipase Substrate Specificity

Controlling the catalytic properties of enzymes remain an important challenge in chemistry and biotechnology. We have recently established a strategy for altering enzyme specificity in which the addition of proxy monobodies, synthetic binding proteins, modulates the specificity of an otherwise unmodified enzyme. Here, in order to examine its broader applicability, we employed the strategy on Candida rugosa lipase 1 (CRL1), an enzyme with a tunnel-like substrate binding site. We successfully identified proxy monobodies that restricted the substrate specificity of CRL1 toward short-chain fatty acids. The successes with this enzyme system and a β-galactosidase used in the previous work suggest that our strategy can be applied to diverse enzymes with distinct architectures of substrate binding sites.

Specific Inter-residue Interactions as Determinants of Human Monoacylglycerol Lipase Catalytic Competency: A ROLE FOR GLOBAL CONFORMATIONAL CHANGES

The serine hydrolase monoacylglycerol lipase (MGL) functions as the main metabolizing enzyme of 2-arachidonoyl glycerol, an endocannabinoid signaling lipid whose elevation through genetic or pharmacological MGL ablation exerts therapeutic effects in various preclinical disease models. To inform structure-based MGL inhibitor design, we report the direct NMR detection of a reversible equilibrium between active and inactive states of human MGL (hMGL) that is slow on the NMR time scale and can be modulated in a controlled manner by pH, temperature, and select point mutations. Kinetic measurements revealed that hMGL substrate turnover is rate-limited across this equilibrium. We identify a network of aromatic interactions and hydrogen bonds that regulates hMGL active-inactive state interconversion. The data highlight specific inter-residue interactions within hMGL modulating the enzymes function and implicate transitions between active (open) and inactive (closed) states of the hMGL lid domain in controlling substrate access to the enzymes active site.

Modeling of solvent-dependent conformational transitions in Burkholderia cepacia lipase

BACKGROUND

The characteristic of most lipases is the interfacial activation at a lipid interface or in non-polar solvents. Interfacial activation is linked to a large conformational change of a lid, from a closed to an open conformation which makes the active site accessible for substrates. While for many lipases crystal structures of the closed and open conformation have been determined, the pathway of the conformational transition and possible bottlenecks are unknown. Therefore, molecular dynamics simulations of a closed homology model and an open crystal structure of Burkholderia cepacia lipase in water and toluene were performed to investigate the influence of solvents on structure, dynamics, and the conformational transition of the lid.

RESULTS

The conformational transition of B. cepacia lipase was dependent on the solvent. In simulations of closed B. cepacia lipase in water no conformational transition was observed, while in three independent simulations of the closed lipase in toluene the lid gradually opened during the first 10-15 ns. The pathway of conformational transition was accessible and a barrier was identified, where a helix prevented the lid from opening to the completely open conformation. The open structure in toluene was stabilized by the formation of hydrogen bonds.In simulations of open lipase in water, the lid closed slowly during 30 ns nearly reaching its position in the closed crystal structure, while a further lid opening compared to the crystal structure was observed in toluene. While the helical structure of the lid was intact during opening in toluene, it partially unfolded upon closing in water. The closing of the lid in water was also observed, when with eight intermediate structures between the closed and the open conformation as derived from the simulations in toluene were taken as starting structures. A hydrophobic beta-hairpin was moving away from the lid in all simulations in water, which was not observed in simulations in toluene. The conformational transition of the lid was not correlated to the motions of the beta-hairpin structure.

CONCLUSION

Conformational transitions between the experimentally observed closed and open conformation of the lid were observed by multiple molecular dynamics simulations of B. cepacia lipase. Transitions in both directions occurred without applying restraints or external forces. The opening and closing were driven by the solvent and independent of a bound substrate molecule.

Understanding Candida rugosa lipases: an overview

Candida rugosa lipase (CRL) is one of the enzymes most frequently used in biotransformations. However, there are some irreproducibility problems inherent to this biocatalyst, attributed either to differences in lipase loading and isoenzymatic profile or to other medium-engineering effects (temperature, a(w), choice of solvent, etc.). In addition, some other properties (influence of substrate and reaction conditions on the lid movement, differences in the glycosylation degree, post-translational modifications) should not be ruled out. In the present paper the recent developments published in the CRL field are overviewed, focusing on: (a) comparison of structural and biochemical data among isoenzymes (Lip1-Lip5), and their influence in the biocatalytical performance; (b) developments in fermentation technology to achieve new crude C. rugosa lipases; (c) biocatalytical reactivity of each isoenzyme, and methods for characterising them in crude CRL; (d) state-of-the-art of new applications performed with recombinant CRLs, both in CRL-second generation (wild-type recombinant enzymes), as well as in CRL-third generation, (mutants of the wt-CRL).

The active component in the flax-retting system of the zygomycete Rhizopus oryzae sb is a family 28 polygalacturonase

The zygomycete Rhizopus oryzae sb is a very efficient organism for retting of flax, the initial microbiological step in the process of making linen. An extracellular polygalacturonase, when isolated could perform retting, and therefore probably is the key component in the retting system of R. oryzae. This was purified and characterized. The purified enzyme has a molecular mass of 37,436 Da from mass spectrometric determination, an isoelectric point of 8.4, and has non-methylated polygalacturonic acid as its preferred substrate. Peptide sequences indicate that the enzyme belongs to family 28, in similarity with other polygalacturonases (EC. 3.2.1.15). It contains, however an N-terminal sequence absent in other fungal pectinases, but present in an enzyme from the phytopathogenic bacterium Ralstonia solanacearum. The biochemical background for the superior retting efficiency of R. oryzae sb is discussed.

A novel lipase/acyltransferase from the yeast Candida albicans: expression and characterisation of the recombinant enzyme

A gene encoding an extracellular lipase (CaLIP4) from Candida albicans was successfully expressed in Saccharomyces cerevisiae after mutagenesis of its unusual CUG serine codon into a universal one. The ability of this lipase, which shares 60% sequence homology with the lipase/acyltransferase from Candida parapsilosis, to synthesise esters was investigated. CaLIP4 behaved as a true lipase, displaying activity towards insoluble triglycerides and having no activity in the presence of short-chain fatty acid (FA) esters and phosphatidylcholine. Methyl, ethyl and propyl esters were efficiently used. The lipase exhibited highest selectivity for unsaturated FA. With saturated FAs, C14-C16 acyl chains were preferred. In a biphasic aqueous/lipid system, CaLIP4 displayed a high alcoholysis activity with a range of alcohols (e.g. methanol, ethanol, propanol and isopropanol) as acyl acceptor. During the course of the alcoholysis reaction, new esters are produced at concentrations above the thermodynamic equilibrium of the esterification reaction, indicating that ester synthesis does not proceed by esterification but mainly by direct acyltransfer. Ester synthesis is under kinetic control due to the high rate of alcoholysis. Unwanted hydrolysis is limited by competition between the acyl acceptor (alcohol) and water for the acyltransfer reaction, favouring the alcohol.

Polymerization of propyl malolactonate in the presence of Candida rugosa lipase

To gain better insight into mechanistic features of enzyme-catalyzed malolactonate polymerization, reactions with propyl malolactonate were analyzed while varying enzyme concentration, reaction media composition, and reaction temperature. Monomer conversion and product molecular weights were characterized by (1)H NMR and MALDI-TOF MS, respectively. A high extent of thermal polymerization of propyl malolactonate was observed, while the polymer chain length in all reactions was controlled by the elimination of alpha-hydrogen from propyl malolactonate with formation of a new initiator and the new chains. The most efficient enzymatic catalysis occurred in toluene (2.11 M monomer) at 60 degrees C. Candida rugosa lipase (10 wt %) accelerated polymerization 25-fold over the rate of thermal polymerization. The maximum poly(propyl malate) number-average molecular weight obtained was 5000 Da at 20 wt % enzyme with a polydispersity of 1.15. These values compare with 1800 Da and 1.5, respectively, in the absence of enzyme.

Influence of the conformational flexibility on the kinetics and dimerisation process of two Candida rugosa lipase isoenzymes

We have investigated the interfacial activation process of two isoenzymes from Candida rugosa (Lip1 and Lip3) using triacetin as substrate. Kinetics were coupled to inhibition experiments in order to analyse the transition between the open and closed conformers. This process was slow, particularly for Lip1, in the absence of an interface provided by the substrate or a detergent. Dimers of Lip3 were also purified and their catalytic action was closer to that of a typical esterase. In spite of the high sequence homology between Lip1 and Lip3, small changes enhance hydrophobicity in the binding pocket of Lip3 and increase the flexibility of its flap. We postulated that these factors account for the higher tendency of Lip3 to dimerise fixing its open conformation.