Kinetic studies of Rhizopus oryzae lipase using monomolecular film technique

Rhizopus oryzae lipase (ROL) was found to be a true lipase. This enzyme presents the interfacial activation phenomenon. The N-terminal amino acid sequence of ROL was compared to those of rhizopus lipases. Purified ROL possesses the same N-terminal sequence as the mature Rhizopus niveus lipase (RNL). This sequence was found in the last 28 amino acids of the propeptide sequence derived from the cDNA of Rhizopus delemar lipase (RDL). Using the baro-stat method, we have measured the hydrolysis rate of dicaprin films by ROL as a function of surface pressure. Our results show that Rhizopus oryzae lipase is markedly stereoselective of the sn-3 position of the 2,3 enantiomer of dicaprin. Polyclonal antibodies (PAB) directed against ROL have been produced and purified by immunoaffinity. The effects of these PAB on the interfacial behavior of ROL were determined. The immunoblot analysis with polyclonal antibodies anti-ROL (PAB anti-ROL) and various lipases shows a cross-immunoreactivity between the lipase from the rhizopus family (Rhizopus delemar lipase and Rhizopus arrhizus lipase).     

Inhibition of lipases by proteins: a binding study using dicaprin monolayers

We previously reported that the inhibition of pancreatic and Rhizopus delemar lipases by proteins is due to the protein associated with lipid and is not caused by direct protein-enzyme interaction in the aqueous phase [Gargouri, Y., Piéroni, G., Rivière, C., Sugihara, A., Sarda, L., & Verger, R. (1985) J. Biol. Chem. 260, 2268-2273]. In this study, using radiolabeled lipases, serum albumin, and beta-lactoglobulin A, we investigated their respective binding with respect to lipolysis of dicaprin monolayers. Lipase inhibition was found to be correlated with a lack of lipase binding to mixed protein-dicaprin films or to a desorption of lipase from the interface when inhibitory protein was added later. Since a large proportion of the lipid film remained potentially accessible to the enzyme in the presence of inhibitory protein, it was concluded that the observed decrease in lipase binding to the interface was due to a variation of the physiochemical properties of the lipid-water interface following binding of inhibitory protein. On the basis of the results presented here, it is proposed that mixed protein-glyceride films could be used to characterize the interaction of various lipases with lipid substrates and to classify these enzymes according to their penetration power.     

Inhibition of pancreatic and microbial lipases by proteins

We have compared the effect of several proteins, including melittin, beta-lactoglobulin A, serum albumin, ovalbumin and myoglobin, on the hydrolysis of tributyrin and triolein by lipases from various origins. All proteins tested inactivate pancreatic lipase in absence of colipase and bile salt. Inhibition is not significantly reversed by colipase in absence of bile salt except in systems containing tributyrin and melittin or triolein and beta-lactoglobulin A. In all other cases, activation of pancreatic lipase by colipase in presence of inhibitory protein requires the presence of bile salt. Lipase from Rhizopus delemar is also inhibited by the proteins that inactivate pancreatic lipase. In contrast, the activity of lipase from Rhizopus arrhizus is not affected by the proteins in the same concentration range. Inhibition of lipase activity by amphiphiles such as proteins or detergents appears to be a general phenomenon not directly related to a decrease in tension at the triacylglycerol-water interface. Inhibition could be the result of desorption of lipase from its substrate due to a change in interfacial quality.     

Kinetic properties of turkey pancreatic lipase: a comparative study with emulsified tributyrin and monomolecular dicaprin

Using the classical emulsified system and the monomolecular film technique, we compared several interfacial properties of turkey pancreatic lipase (TPL) and human pancreatic lipase (HPL). TPL, like HPL, presented the interfacial activation phenomenon when vinyl ester was used as substrate. In the absence of colipase and bile salts, using tributyrin emulsion or monomolecular films of dicaprin at low surface pressure, TPL, unlike HPL, hydrolyzes pure tributyrin emulsion as well as dicaprin films maintained at low surface pressures. TPL was also able to hydrolyze triolein emulsion in the absence of any additive and despite the accumulation of long-chain free fatty acids at the interface. The difference of behaviors between TPL and HPL can be explained by the penetration power of each enzyme. The enzyme that presents the maximal pi(c) (TPL) interacts more efficiently with interfaces, and it is not denaturated at high interfacial energy. Turkey pancreatic lipase is more active on rac-dicaprin than HPL; a maximal ratio of 9 was found between the catalytic activities of the two lipases measured at their surface pressure optima (20 mN m(-1)). A kinetic study on the surface pressure dependency, stereospecificity, and regioselectivity of TPL was performed using enantiopure diglyceride (1,2-sn-dicaprin and 2,3-sn-dicaprin) and a prochiral isomer (1,3-dicaprin) that were spread as monomolecular films at the air-water interface. At low surface pressure (15 mN m(-1)), TPL acts preferentially on primary carboxylic ester groups of the diglyceride isomers (1,3-dicaprin), but at high surface pressure (23 mN m(-1)), this enzyme prefers both adjacent ester groups of the diglyceride isomers (1,2-sn-dicaprin and 2,3-sn-dicaprin). HPL prefers adjacent ester groups of the diglyceride isomers (1,2-sn-dicaprin and 2,3-sn-dicaprin). Furthermore, TPL was found to be markedly stereospecific for the sn-1 position of the 1,2-sn-enantiomer of dicaprin at low surface pressure (15 mN m(-1)), while at high surface pressure (23 mN m(-1)), this lipase presents a stereopreference for the sn-3 position of the 2,3-sn-enantiomer of dicaprin. HPL is stereospecific for the sn-1 position of the 1,2-sn-enantiomer of dicaprin both at 15 and 23 mN m(-1).     

Synthesis of various kinds of esters by four microbial lipases

Ester synthesis by microbial lipases, using homogeneous enzyme preparations, were investigated. The amount of synthesized ester was estimated by alkalimetry, and products were identified by thin-layer chromatography and infrared spectroscopy. Lipases from Aspergillus niger, Rhizopus delemar, Geotrichum candidum and Penicillium cyclopium synthesized esters from oleic acid and various primary alcohols. Only Geotrichum candidum lipase synthesized esters of secondary alcohols. Esters of tertiary alcohols, phenols or sugar alcohols were not synthesized by any lipase. Rather high concentrations of alcohol were required to synthesize the esters of ethylene glycol, propylene glycol or trimethylene glycol. Lipases from Aspergillus niger and Rhizopus delemar synthesized oleyl esters of various fatty acids and some dibasic acids. In contrast, lipases from Geotrichum candidum and Penicillium cyclopium synthesized oleyl esters only from medium or long chain fatty acids.     

Inhibition of lipases from Chromobacterium viscosum and Rhizopus oryzae by tetrahydrolipstatin

Tetrahydrolipstatin is known as an inhibitor for pancreatic lipase but not for microbial lipases. In this paper we demonstrate that in the presence of water-insoluble substrates like tributyrin or olive oil, tetrahydrolipstatin inhibits the lipases of Chromobacterium viscosum and Rhizopus oryzae, although with different potency. In contrast to porcine pancreatic lipase, which forms an irreversible and covalent enzyme-inhibitor complex with tetrahydrolipstatin, the inhibition of the microbial lipases is reversible as the inhibitor can be removed from the enzyme-inhibitor complex by solvent extraction. Moreover, after inhibition of Chromobacterium viscosum lipase tetrahydrolipstatin remains chemically unchanged.     

Esterification reactions catalyzed by lipases in microemulsions: the role of enzyme localization in relation to its selectivity

The activity of lipases from Rhizopus delemar, Rhizopus arrhizus, and Penicillium simplicissimum entrapped in microemulsions formulated by bis-(2-ethylhexyl)sulfo-succinate sodium salt (AOT) in isooctane has been studied in esterification reactions of various aliphatic alcohols with fatty acids. The effect of the nature of the fatty acids (chain length) and of the alcohols (primary, secondary, or tertiary; chain length; cyclic structures) on the lipase activities was investigated in relation to the reverse micellar structure. The lipases tested showed a selectivity regarding the structure of the substrates used when hosted in the AOT/isooctane microemulsion systems. Penicillium simplicissimum lipase showed higher reaction rates in the esterification of long chain alcohols as well as secondary alcohols. Primary alcohols had a low reaction rate and tertiary a very slow rate of esterification. Long chain fatty acids were better catalyzed as compared to the shorter ones. Rhizopus delemar and R. arrhizus lipases showed a preference for the esterification of short chain primary alcohols, while the secondary alcohols had a low rate of esterification and the tertiary ones could not be converted. The reaction of medium chain length fatty acids was also better catalyzed than in the case of the long ones. The observed lipase selectivity appeared to be related to the localization of the enzyme molecule within the micellar microstructure due to the hydrophobic/hydrophilic character of the protein. The reverse micellar structural characteristics, as well as the localization of the enzyme, were examined by fluorescence quenching measurements and spectroscopical studies. (c) 1993 John Wiley & Sons, Inc.     

Eukaryotic Expression System Pichia pastoris Affects the Lipase Catalytic Properties: A Monolayer Study

Recombinant DNA methods are being widely used to express proteins in both prokaryotic and eukaryotic cells for both fundamental and applied research purposes. Expressed protein must be well characterized to be sure that it retains the same properties as the native one, especially when expressed protein will be used in the pharmaceutical field. In this aim, interfacial and kinetic properties of native, untagged recombinant and tagged recombinant forms of a pancreatic lipase were compared using the monomolecular film technique. Turkey pancreatic lipase (TPL) was chosen as model. A kinetic study on the dependence of the stereoselectivity of these three forms on the surface pressure was performed using three dicaprin isomers spread in the form of monomolecular films at the air-water interface. The heterologous expression and the N-His-tag extension were found to modify the pressure preference and decrease the catalytic hydrolysis rate of three dicaprin isomers. Besides, the heterologous expression was found to change the TPL regioselectivity without affecting its stereospecificity contrary to the N-tag extension which retained that regioselectivity and changed the stereospecificity at high surface pressures. The study of parameters, termed Recombinant expression Effects on Catalysis (REC), N-Tag Effects on Catalysis (TEC), and N-Tag and Recombinant expression Effects on Catalysis (TREC) showed that the heterologous expression effects on the catalytic properties of the TPL were more deleterious than the presence of an N-terminal tag extension.     

Kinetic Properties of a Novel Fusarium solani (phospho)lipase: A Monolayer Study

Using the monomolecular film technique, we studied interfacial properties of Fusarium solani lipase (FSL). This lipolytic enzyme was found to be unique among the fungal lipases possessing not only a lipase activity but also a high phospholipase one.The FSL was able to hydrolyze dicaprin films at various surface pressures. The surface pressure dependency, the stereospecificity, and the regioselectivity of FSL were performed using optically pure stereoisomers of diglyceride (1,2‐sn‐ dicaprin and 2,3‐sn‐dicaprin) and a prochiral isomer (1,3‐sn‐dicaprin) spread as monomolecular films at the air–water interface. The FSL prefers adjacent ester groups of the diglyceride isomers (1,2‐sn‐dicaprin and 2,3‐sn‐dicaprin) at low and high surface pressures. Furthermore, FSL was found to be markedly stereospecific for the sn‐1 position of the 1,2‐sn‐enantiomer of dicaprin at both low and high surface pressures.Moreover, FSL shows high activities on phospholipids monolayers. However, this enzyme displays high preference to zwitterionic phospholipids compared to the negatively charged ones. Chirality, 25:35‐38, 2012. © 2012 Wiley Periodicals, Inc.     

Glyceride synthesis by four kinds of microbial lipase

Apart from their usual mechanism of action, lipases from Aspergillus niger and Rhizopus delemar also catalyzed the synthesis of glycerides from oleic acid and glycerol. Lipases from Geotrichum candidum and Penicillium cyclopium were inactivated by oleic acid, but were stable in the presence of casein, albumin or buffer of appropriate pH. Lipases from Aspergillus niger and Rhizopus delemar synthesized glycerides from, not only fatty acid, but dibasic acids and aromatic acids, making ester bonds only at position 1 and 3 of glycerol. In contrast, lipases from Geotricum candidum and Penicillium cyclopium synthesized glycerides only from long chain fatty acids, and made ester bonds at all three available positions of the glycerol molecule.     

Role of a sulfhydryl group in gastric lipases. A binding study using the monomolecular-film technique

Native human and rabbit gastric lipases (HGL and RGL, respectively) were inactivated after modification of one sulfhydryl group/enzyme molecule. HGL and RGL were covalently labeled using 5,5'-dithiobis(2-nitro-[14C]benzoic acid) and the interaction of 2-nitro-5-thio-[14C]benzoic-acid-labeled lipases ([14C]Nbs-lipases) with monomolecular lipid films was investigated. Our results show that [14C]Nbs-lipases bind to lipid films as efficiently as native HGL or RGL. The critical surface pressure pi c and the maximal surface pressure (delta pi max) of [14C]Nbs-lipases were enhanced in comparison with those of native RGL and HGL. These changes in behavior were probably due to an increase in hydrophobicity brought about, directly or indirectly, by the binding of the Nbs radical. This chemical modification thus blocks the hydrolysis site and reinforces the hydrophobic character of the gastric lipases.     

Lipase hydrolysis of mammalian long-chain 1,2-alkanediol diesters. Nonrandom distribution of fatty acids

Long-chain 1,2-alkanediol diesters were isolated from the total surface lipids of golden Syrian hamsters and Swiss albino mice. Hydrolysis of the diol diester waxes with exocellular lipase from Rhizopus arrhizus delemar or with purified porcine pancreatic lipase produced free fatty acids and 2-acyl diols in about 60--80% yield. Nonrandom distribution of the constituent fatty acids at positions 1 and 2 of the alkanediols was observed. In the diester waxes from the hamster, both straight-chain and branched-chain fatty acids of 14 to 20 carbon atoms predominated at position 1 and those of 22 to 26 carbon atoms at position 2. In contrast, the diester waxes of the mouse contained mainly fatty acids of less than 19 carbon atoms, both saturated and monounsaturated, at position 2 and those of greater chain length (20 to 24 carbon atoms) at position 1. The results of the lipase hydrolysis were confirmed by degradation of the diester waxes with Grignard reagent.     

Lipid-lipid interactions as regulators of carboxylester lipase activity

The hydrolysis of 1,3-dioleoylglycerol and related substrates by mammalian pancreatic carboxylester lipases was studied. Mixed lipid films of substrates with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine at the argon-buffer interface were exposed to relatively high levels of monomeric porcine pancreatic carboxylester lipase for a brief period. With either 1,3-dioleoylglycerol, 1,2-dioleoylglycerol, trioleoylglycerol, or oleoylmethanol as a substrate, the percentage of substrate hydrolysis increased abruptly from near zero to near 100% with increasing proportion of substrate in the film. The phospholipid was not hydrolyzed. Using 1,3-dioleoylglycerol as the substrate with either the dimeric, porcine pancreatic carboxylester lipase, human pancreatic carboxylester lipase, or human milk bile salt-stimulated lipase gave results identical to those obtained with the porcine monomer. Hydrolysis of 1,3-dioleoylglycerol by porcine monomeric carboxylester lipase was independent of the initial surface pressure of the film. However, a strong correlation was observed between hydrolysis and interfacial lipid composition at all surface pressures, even if bulk 1,3-dioleoylglycerol was also present. The ultrasensitive dependence of hydrolysis on interfacial lipid composition, i.e. lipid-lipid interactions, suggests that such "switching" may contribute to the regulation of diacylglycerol levels in cells where they function in signal transduction.     

Adsorption Properties and Activities of Lipase on a Gold Substrate Modified by Self-assembled Monolayers

The adsorption properties, amount and specific activity of lipase D from Rhizopus delemar were investigated by employing a gold substrate modified with seven kinds of thiol monolayer. Quartz crystal microbalance measurements revealed that the amount of the enzyme adsorbed to the hydrophobic monolayers (e.g. benzenethiol) was much higher than that to the hydrophilic monolayers (e.g. 3-mercaptopropanoic acid). In contrast, lipase D adsorbed to the hydrophilic, 2-amino-1-ethanethiol monolayer showed the highest specific activity, the value being 300-fold higher than for the same enzyme dissolved in an aqueous medium.     

Adsorption properties and activities of lipase on a gold substrate modified by self-assembled monolayers.

The adsorption properties, amount and specific activity of lipase D from Rhizopus delemar were investigated by employing a gold substrate modified with seven kinds of thiol monolayer. Quartz crystal microbalance measurements revealed that the amount of the enzyme adsorbed to the hydrophobic monolayers (e.g. benzenethiol) was much higher than that to the hydrophilic monolayers (e.g. 3-mercaptopropanoic acid). In contrast, lipase D adsorbed to the hydrophilic, 2-amino-1-ethanethiol monolayer showed the highest specific activity, the value being 300-fold higher than for the same enzyme dissolved in an aqueous medium.     

Properties and function of pancreatic lipase related protein 2

The lipase gene family includes pancreatic triglyceride lipase and two pancreatic proteins, pancreatic lipase related proteins 1 and 2, with strong nucleotide and amino acid sequence homology to pancreatic triglyceride lipase. All three proteins have virtually identical three-dimensional structures. Of the pancreatic triglyceride lipase homologues, only pancreatic lipase related protein 2 has lipase activity. Like pancreatic triglyceride lipase, related protein 2 cleaves triglycerides, but it has broader substrate specificity. Pancreatic lipase related protein 2 also hydrolyzes phospholipids and galactolipids, two fats that are not substrates for pancreatic triglyceride lipase. The rat-related protein 2 also differs from pancreatic triglyceride lipase in sensitivity to bile salts and in response to colipase. Although the pancreas expresses both lipases, their temporal pattern of expression differs. Pancreatic lipase-related protein 2 mRNA appears before birth and persists into adulthood, whereas PTL mRNA first appears at the suckling-weanling transition. Additionally, intestinal enterocytes, paneth cells and cultured cytotoxic T-cells express mRNA encoding pancreatic lipase related protein 2. A physiological function for pancreatic lipase related protein 2 was demonstrated in mice that did not express this protein. Pancreatic lipase related protein 2 deficient mice malabsorbed fat in the suckling period, but not after weaning. They also had a defect in T-cell mediated cytotoxicity. Thus, pancreatic lipase related protein 2 is a lipase that participates in the cytotoxic activity of T-cells and plays a critical role in the digestion of breast milk fats.     

华根霉脂肪酶有机相合成酶活的研究

通过比较7种微生物脂肪酶的有机相合成酶活、水相水解酶活及在正庚烷中催化己酸乙酯合成的能力,证明了合成酶活与水解酶活相关性不高,合成酶活比水解酶活更能反映脂肪酶的合成能力。通过比较两株华根霉(Rhizopus chinensis)脂肪酶酶活,发现合成酶活相差较大,表明相同种属微生物的脂肪酶合成酶活存在不同。对．Rhizopus chinensis-2液态发酵产脂肪酶进程研究发现,水解酶活高峰先于合成酶活高峰大约12h。将不同培养时间的Rhizopus chinensis-2全细胞脂肪酶用于催化己酸乙酯合成,具有高合成酶活的全细胞脂肪酶催化己酸乙酯合成反应较快。因此,全细胞脂肪酶用于催化有机相酯合成反应时,具有高脂肪酶合成酶活的菌体具有较好的催化酯合成能力。     

N-terminal peptide of Rhizopus oryzae lipase is important for its catalytic properties

In a culture medium, the Rhizopus oryzae strain produces only one form of lipase, ROL32. When the concentrated culture medium was stored at 0 degrees C during several months or kept at 6 degrees C during a few days, we noticed the appearance of a second shorter form of ROL32 lacking its N-terminal 28 amino acid (ROL29). ROL29 was purified to homogeneity and its 21 N-terminal amino acid residues were found to be identical to the 29-49 sequence of ROL32. The cleavage of the N-terminal peptide reduced the specific activity of ROL29 by 50% using either triolein or tributyrin as substrates. In order to explain this decrease of the specific activity of ROL29, we measured its critical surface pressure of penetration into phosphatidyl choline from egg yolk films which was found to be 10 mN/m, in contrast to a value of 23 mN/m found in ROL32. A kinetic study on the surface pressure dependency, stereoselectivity and regioselectivity of ROL29 was performed using the three dicaprin isomers spread as monomolecular films at the air-water interface. Our results showed that in contrast to ROL32, ROL29 presented a preference for the distal ester groups of one diglyceride isomer (1,3-sn-dicaprin). Furthermore, ROL32 was markedly more stereoselective than ROL29 for the sn-3 position of the 2,3-sn-enantiomer of dicaprin. A structural explanation of the enhanced penetration capacity as well as the catalytic activity of ROL32 was proposed by molecular modeling. We concluded that the N-terminal peptide of ROL32 can play an important role in the specific activity, the regioselectivity, the stereoselectivity and the binding of the enzyme to its substrate.     

Green tea extract (AR25) inhibits lipolysis of triglycerides in gastric and duodenal medium in vitro

In this study, we aimed to evaluate in vitro the inhibitory activity of a green tea extract (AR25 standardized at 25% catechins) on gastric and pancreatic lipase activities. We first used tributyrin as a substrate to evaluate the capability of AR25 to induce digestive lipase inhibition. Gastric lipase was totally inhibited by 40 mg AR25/g tributyrin whereas pancreatic lipase inhibition was maximum (78.8 +/- 0.7%) with 80 mg AR25/g tributyrin. We then used triolein, a long-chain triglyceride, to check whether AR25 could alter lipase activities on a physiologic substrate. AR25 60 mg/g triolein induced a dramatic inhibition of gastric lipase (96.8 +/- 0.4%) whereas pancreatic lipase activity was partially reduced (66.50 +/- 0.92%). Finally, the concerted action of gastric and pancreatic lipases was studied with an excess of enzymes to mimic the physiologic conditions observed in vivo. Incubation of AR25 with an excess of digestive lipases resulted in a drastic decrease in gastric lipolysis but the inhibitory effect on pancreatic lipase was less marked. On the whole, as compared to the control, lipolysis of triolein under the successive action of the two digestive lipases was reduced by 37 +/- 0.6% in the presence of AR25. Because a lipid/water interface is necessary for lipolysis to occur, lipid emulsification and emulsion droplet size were measured in gastric and duodenal media in the presence of AR25. In gastric and duodenal conditions, AR25 inhibited the lipid emulsification process. From these data we conclude that (1) in vitro, fat digestion is significantly inhibited by 60 mg AR25/g triolein, and (2) gastric as well as pancreatic lipase inhibition could be related to altered lipid emulsification in gastric or duodenal media. The green tea extract AR25 exhibiting marked inhibition of digestive lipases in vitro is likely to reduce fat digestion in humans.