J. Rathelot

Bio: J. Rathelot is an academic researcher from University of Provence. The author has contributed to research in topics: Colipase & Lipase. The author has an hindex of 15, co-authored 23 publications receiving 722 citations.

Studies on the Effect of Bile Salt and Colipase on Enzymatic Lipolysis. Improved Method for the Determination of Pancreatic Lipase and Colipase

Abstract: The rate of hydrolysis of long chain triglycerides by pure bovine pancreatic lipase has been determined in the presence of variable amounts of bile salts and colipase. Cofactor-free lipase is strongly inhibited by sodium taurodesoxycholate and by mixed bovine bile salts at concentrations higher than the critical micellar concentration. Bile salt inhibited lipase is reactivated by the addition of bovine colipase. Gel filtration of pancreatic juice from several species (Cow, dog, pig) on Sephadex G 100 allows the separation of lipase from colipase. It is found that the enzyme catalyzed hydrolysis of long chain triglycerides by pancreatic lipase from one species is activated by the addition of colipase from other species. Studies on the activation of pancreatic lipase by colipase in the presence of bile salts allowed the re-evaluation of optimal conditions for the determination of lipase and the development of a procedure to assay colipase.

Horse pancreatic lipase. Interaction with colipase from various species.

Abstract: Horse pancreatic lipase has been purified from tissue homogenates. Molecular and catalytic properties of horse lipase are comparable to those of the pancreatic lipases previously isolated. Kinetic studies of the inhibition of horse lipase activity by bile salts and of reactivation by pure colipase from three species (horse, ox and pig) allowed to calculate the apparent dissociation constant (Kd) of the lipase-colipase complex in the presence of the substrate (triolein). Identical values of Kd were found in all three cases (Kd = 1.1 10(-9) M). These values are lower by several orders of magnitude than that published for the binding between lipase and colipase in the absence of substrate. Qualitative experiments show that the activation of horse lipase can be accomplished by rat, dog and chicken colipase as well. The interaction between lipase and colipase is enhanced when the complex is adsorbed at the lipid-water interface. This specific protein-protein interaction is preserved in heterologous mixtures using colipases from other animal species.

Pancreatic and microbial lipases: A comparison of the interaction of pancreatic colipase with lipases of various origins

Abstract: Conjugated bile salts inhibit the hydrolysis of triglycerides (TG) by the lipases fromRhizopus arrhizus andGeotrichum candidum. This occurs for detergent concentrations similar to those which suppress the action of mammalian pancreatic lipases upon the same substrates. However, in opposition with what is observed with the latter enzymes, the activity is not restored by the addition of pancreatic colipase. Both pancreatic andR. arrhizus lipases are inactivated at tributyrin/water interface, but only the first enzyme is protected against this surface denaturation by the pancreatic cofactor. These observations suggest that colipases synthesized in mammalian pancreas display specific interaction towards the lipases made by the same organ.

Studies on bovine pancreatic lipase and colipase

Abstract: 1. 1. Purification of bovine pancreatic lipase (glycerol-ester hydrolase, EC 3.1.1.3) was achieved from pancreas and pancreatic juice. Purification includes (NH4)2SO4 fractionation, chromatography on DEAE-cellulose at pH 7.0 and CM-cellulose at pH 5.0 and gel filtration on Sephadex G-100. Gel filtration allowed an estimated molecular weight of the enzyme as 48500. 2. 2. Purified bovine lipase displays partial activity toward emulsified short and long chain triglycerides. Maximal activity is reached upon addition of a fraction separated from the enzyme during the DEAE-cellulose chromatography. Properties of this fraction are analogous to those of the already well characterized porcine cofactor of lipase (colipase). Porcine and bovine colipase are equally effective for activation of bovine lipase. From the observed effect of colipase on maximum rate of hydrolysis of emulsified triglycerides, it is suggested that the cofactor might be involved in the rate-limiting step of lipolysis.

Characterization of Triton X 100 extracted colipase from porcine pancreas.

Abstract: Summary Colipase was isolated from porcine pancreas homogenate prepared in the presence of detergent (Triton X 100). After precipitation by ammonium sulfate and ethanol, the cofactor was purified by chromatography on SP-Sephadex in the presence of Triton X 100 and on DEAE-cellulose in the absence of detergent. Two molecular forms of porcine colipase were obtained. They represent 80 per cent (colipase A) and 20 per cent (colipase B), respectively, of the total colipase. Valine is the N-terminal residue of both proteins. Their aminoacid composition is similar to that found by Borgstrom for the two forms of porcine colipase. Determination of the sequence of the first sixteen residues at the N-terminal end of colipase A indicates that the cofactor undergoes no proteolytic degradation in this region of the molecule when extraction is carried out in the presence of detergent. The recovery of colipase is about 30 per cent.

Lipases at interfaces : a review

Abstract: Lipases are acyl hydrolases that play a key role in fat digestion by cleaving long-chain triglycerides into polar lipids Due to an opposite polarity between the enzyme (hydrophilic) and their substrates (lipophilic), lipase reaction occurs at the interface between the aqueous and the oil phases Hence, interfaces are the key spots for lipase biocatalysis and an appropriate site for modulating lipolysis Surprisingly enough, knowledge about the effects of the interfacial composition on lipase catalysis is still limited and only described by the term "interfacial quality" Recent systematic studies based on a biophysical approach allowed for the first time to show the effects of the interfacial microenvironment on lipase catalysis These studies demonstrate that lipase activity as a function of interfacial composition is more attributed to substrate inaccessibility rather than to enzyme denaturation or inactivation, as it is often hypothesized A detailed analysis of the interfacial properties of all compounds involved in triglyceride digestion revealed that lipolysis is a self-regulated reaction This feedback mechanism can be explored as a new avenue to control lipase catalysis To substantiate this hypothesis, oil hydrolysis in a model gastro-intestinal system was performed, which can be seen as an interfacial engineering approach to enzyme reactivity control The presented characterization of the interfacial composition and its consequences provide a new approach for the understanding of lipase reactions at interfaces with direct impact on biotechnological and health care applications

Structure of the pancreatic lipase-procolipase complex

Abstract: Interfacial adsorption of pancreatic lipase is strongly dependent on the physical chemical properties of the lipid surface. These properties are affected by amphiphiles such as phospholipids and bile salts. In the presence of such amphiphiles, lipase binding to the interface requires a protein cofactor, colipase. We obtained crystals of the pancreatic lipase-procolipase complex and solved the structure at 3.04 A resolution. Here we describe the structure of procolipase, which essentially consists of three 'fingers' and is topologically comparable to snake toxins. The tips of the fingers contain most of the hydrophobic amino acids and presumably form the interfacial binding site. Lipase binding occurs at the opposite side to this site and involves polar interactions. Determination of the three-dimensional structure of pancreatic lipase has revealed the presence of two domains: an amino-terminal domain, at residues 1-336 containing the active site and a carboxy-terminal domain at residues 337-449 (ref. 6). Procolipase binds exclusively to the C-terminal domain of lipase. No conformational change in the lipase molecule is induced by the binding of procolipase.

Present and future applications of lipases

Abstract: (1985). Present and Future Applications of Lipases. Biotechnology and Genetic Engineering Reviews: Vol. 3, No. 1, pp. 193-218.

Pancreatic lipase and co-lipase. Interactions and effects of bile salts and other detergents.

Abstract: The effect of conjugated bile salts on the activity of pancreatic lipase depends on their concentration in relation to their critical micellar concentration. Below the critical micellar concentration, conjugated bile salts slightly stimulate the initial rate of hydrolysis of tributyrine, an effect that may be caused by a protection of the enzyme from inactivation at the substrate-water interface. Above the critical micellar concentration, conjugated bile salts almost completely inhibit lipase. The inhibition is more marked in alkaline reactions resulting in a pH optimum shift with increasing bile salt concentration. Bile salt inhibition of lipase is related both to the concentration of bile salt and to the substrate concentration or rather to substrate surface area, and most probably is complete when the interface is saturated with detergent. Co-lipase, in the absence of bile salts, stimulates the activity of lipase, 1.3 to 1.4-fold in the whole pH range of its activity. Co-lipase overcomes the inhibition of lipase caused by bile salts with a shift in the pH optimum to 6–7 compared to 8–9 for lipase alone. The different conjugated bile salts have similar effects, consideration being taken to differences in their critical micellar concentration; free bile salts have a less inhibitory effect on lipase and the stimulation by co-lipase shows no pH optimum shift. Detergents of the acyltaurine type such as decanoyltaurine and dodecanoylsarcosyltaurine inhibit lipase in a similar manner to the conjugated bile salts and this inhibition is also released by co-lipase. Detergents such as dodecylsulphate above the micellar concentration, irreversibly inhibit lipase. The simultaneous presence of bile salts protects the enzyme from being irreversibly inactivated. Lipase and co-lipase interact in a stoichiometrical relationship and it appears justified to classify co-lipase as a co-enzyme for lipase.

Kinetics and mechanisms of reactions catalysed by immobilized lipases.

Abstract: This review focuses on the kinetics and mechanisms of reactions catalysed by immobilized lipases. The effects of pH, temperature, and various substances on the catalytic properties of immobilized lipases and on the processes by which they are deactivated are reviewed and discussed.