Screening of stable cutinase from Fusarium solani pisi using plasmid display system

Although enzymes are potential candidates for industrial catalysts, their industrial applications have been limited because they are easily deactivated under harsh operational conditions. In this study, a plasmid display system was used for the screening of stable cutinase in organic solvent (20% acetonitrile) and at high temperature. The fusion proteins were expressed and bound to specific DNA sequences on the encoding plasmids. Proteolysis resistance was used as a selection tool, where well-folded proteins are more resistant to the protease digestion than poorly-folded proteins. Stable mutants, identified to be I183T, I183F, and A56V, were screened in the organic solvent and at high temperature. The I183T and I183F mutants were more stable than the A56V mutant in 20% acetonitrile, while the A56V mutant was superior to the I183T and I183F mutants at high temperature. Molecular modeling was performed in order to investigate the residual characteristics of the stable mutants; secondary structure, residual solvation energy, residual ??-carbon flexibility, number of hydrogen bonds, number of neighboring amino acids, ratio of exposed/buried residue, and surface area. This analysis provided some guidelines for increased stability.     

Stability of a Fusarium solani pisi recombinant cutinase in phosphatidylcholine reversed micelles

Summary A Fusarium solani pisi recombinant cutinase solubilized in phosphatidylcholine/isooctane reversed micelles was used to catalyse the esterification reaction of butyric acid with 2-butanol at pH 10.7. The influence of temperature, Wo and substrates on lipase stability was evaluated. The enzyme displays a better stability, with a half-life over 125 days, at a temperature of 22°C and for a low water content (W_O= 6.5). Butyric acid increased the cutinase deactivation (t_1/2=0.56h), while 2-butanol led to a similar half-life (t_1/2=14h) as without substrate.     

The interaction of Fusarium solani pisi cutinase with long chain spin label esters

We here present a study of the interaction between the Fusarium solani pisi cutinase mutant S120A and spin-labeled 4,4-dimethyloxazoline-N-oxyl-(DOXYL)-stearoyl-glycerol substrates in a micellar system. The interaction is detected by NMR measuring changes in chemical shift for 1H and 15N as well as relaxation parameters for backbone 1H (T1) and 15N (T1, T2) atoms as well as for side chain methyl groups 1H (T1). The detected interaction shows a weak binding of cutinase to the lipid micelles. Structural and mobility changes are located inside and around the active site, its flanking loops, and the oxyanion hole, respectively. Relaxation changes in the amino acid pairs Ser 92, Ala 93 and Thr 173, Gly 174 positioned at the edge of each of the active site flanking loops make these residues prime candidates for hinges, allowing for structural rearrangement during substrate binding. The cutinase mutant S120A used carries a 15 amino acid pro-peptide; the significance of this pro-peptide was so far undetermined. We show here that the pro-peptide is affected by the presence of the micellar substrate. Relaxation enhancements indicative of spatial proximity between the DOXYL group in the lipid chain and some hydrophobic residues surrounding the active site could be found.     

NMR studies of Fusarium solani pisi cutinase in complex with phosphonate inhibitors.

The backbone dynamics of Fusarium solani pisi cutinase in complex with a phosphonate inhibitor has been studied by a variety of nuclear magnetic resonance experiments to probe internal motions on different time scales. The results have been compared with dynamical studies performed on free cutinase. In solution, the enzyme adopts its active conformation only upon binding the inhibitor. While the active site Ser120 is rigidly attached to the stable alpha/beta core of the protein, the remainder of the binding site is very flexible in the free enzyme. The other two active site residues Asp175 and His188 as well as the oxyanion hole residues Ser42 and Gln121 are only restrained into their proper positions upon binding of the substrate-like inhibitor. The flap helix, which opens and closes the binding site in the free molecule, is also fixed in the cutinase-inhibitor complex. Our results are in contrast with the X-ray analysis results, namely that in the protein crystal, free cutinase has a well-defined active site and a preformed oxyanion hole and that it does not need any rearrangements to bind its substrate. Our solution studies show that cutinase does need conformational rearrangements to bind its substrate, which may form the rate-limiting step in catalysis.     

Crystallization and preliminary X-ray study of a recombinant cutinase from Fusarium solani pisi

Recombinant cutinase from Fusarium solani pisi is expressed and excreted with very high yields in Escherichia coli cultures. Cutinase was crystallized at 20 degrees C using the vapour diffusion technique, with polyethylene glycol 6000 as precipitant. Best crystals were obtained at pH 7.0 with polyethylene glycol 6000 as precipitant. Best crystals were obtained at pH 7.0 with polyethylene glycol at 15 to 20%. They are monoclinic, with space group P2(1) and cell dimensions a = 35.1 A, b = 67.4 A, c = 37.05 A and beta = 94.0 degrees; they diffract beyond 1.5 A resolution. The asymmetric unit contains one molecule of 22,000 Da (Vm = 1.98 A3/Da; 38% water).     

Fusarium solani pisi recombinant cutinase partitioning in peg/potassium phosphate aqueous two-phase systems

Summary An aqueous two-phase system of polyethylene glycol (PEG) and potassium phosphate was developed for extraction of a cutinase from cell debris of a recombinant Escherichia coli strain. Basic studies to identify the primary factors which affect cutinase partition, namely the influence of polymer molecular weight, polymer concentration and pH were carried out using a purified preparation of the cutinase. The enzyme partition coefficient was enhanced with decreasing PEG molecular weight, increasing tie-line length and pH.     

Production of Fusarium solani f. sp. pisi cutinase in Fusarium venenatum A3/5

Fusarium venenatum A3/5 was transformed using the Aspergillus niger expression plasmid, pIGF, in which the coding sequence for the F. solani f. sp. pisi cutinase gene had been inserted in frame, with a KEX2 cleavage site, with the truncated A. niger glucoamylase gene under control of the A. niger glucoamylase promoter. The transformant produced up to 21 U cutinase l⁻¹ in minimal medium containing glucose or starch as the primary carbon source. Glucoamylase (165 U l⁻¹ or 8 mg l⁻¹) was also produced. Both the transformant and the parent strain produced cutinase in medium containing cutin.     

Direct evidence for the presence of beta-hydroxyphenylalanine and beta-hydroxytyrosine in cutinase from Fusarium solani pisi

Extracellular cutinase induced by cutin hydrolysate in glucose-grown Fusarium solani f. pisi was isolated in electrophoretically homogeneous form. This enzyme was similar to cutinase I generated by cutin-grown cells in its catalytic properties such as pH optimum, substrate specificity, and inactivation by “active serine”-directed reagents. Its molecular weight was 26,300 and this enzyme had a much larger content of serine and threonine residues than that found in cutinase from the cutin-grown cells. The hydrolysate-induced enzyme was a glycoprotein containing 6% carbohydrates. Alkaline NaB³H₄ treatment of the protein generated labeled protein and labeled carbohydrates. Analyses of the hydrolysates of these labeled products showed that alanine, α-aminobutyrate, phenylalanine, and tyrosine in the protein were labeled strongly suggesting that serine, threonine, β-hydroxyphenylalanine, and β-hydroxytyrosine were involved in O-glycosidic linkages in this protein. The protein hydrolysate also contained labeled gulonic acid, suggesting that d-glucuronic acid was attached to the protein via a base stable linkage, presumably an amide linkage at the N-terminus. The labeled reduced carbohydrates were identified by ion-exchange, thin-layer, gas-liquid, and high-performance liquid chromatographic techniques as mannitol, arabitol, gulonic acid, and 2-aminosorbitol. Thus mannose, arabinose, glucuronic acid, and glucosamine (possibly N-acetylated) were attached O-glycosidically to the hydroxyamino acids. Induction of cutinase by cutin hydrolysate in the presence of tritiated phenylalanine gave labeled cutinase. Cleavage of the O-glycosidically attached carbohydrates by anhydrous HF, followed by enzymatic hydrolysis of the labeled protein, gave rise to labeled amino acids, which upon analysis with an amino acid analyzer revealed four radioactive components. Two of them were identified as phenylalanine and tyrosine, while the other two cochromatographed with authentic β-hydroxyphenylalanine and β-hydroxytyrosine not only by the amino acid analyzer but also upon thin-layer chromatography. These results constitute the first direct evidence for the presence of the novel β-hydroxyaromatic amino acids in a protein.     

DSC studies of Fusarium solani pisi cutinase: consequences for stability in the presence of surfactants

The application of cutinase from Fusarium solani pisi as a fat-stain removing ingredient in laundry washing is hampered by its lack of stability in the presence of anionic surfactants. We postulate that the stability of cutinase towards anionics can be improved by mutations increasing its temperature stability. Thermal unfolding as measured with DSC, appears to be irreversible, though the thermograms are more symmetric than predicted by a simple irreversible model. In the presence of taurodeoxycholate (TDOC), the unfolding temperature is lower and the unfolding is reversible. We conclude that an early reversible unfolding intermediate exists in which a number of additional hydrophobic patches are exposed to the solvent, or preferentially are covered with TDOC. Improvement of the stability of cutinase with respect to both surfactants and thermal denaturation, should thus be directed toward the prevention of exposure of hydrophobic patches in the early intermediate.     

Tryptophan mediated photoreduction of disulfide bond causes unusual fluorescence behaviour of Fusarium solani pisi cutinase.

The fluorescence signal of the single tryptophan residue (Trp69) of Fusarium solani pisi cutinase is highly quenched. However, prolonged irradiation of the enzyme in the tryptophan absorption band causes an increase of the tryptophan fluorescence quantum yield by an order of magnitude. By using a combination of NMR spectroscopy and chemical detection of free thiol groups with a sulfhydryl reagent we could unambiguously show that the unusual fluorescence behaviour of Trp69 in cutinase is caused by the breaking of the disulfide bond between Cys31 and Cys109 upon irradiation, while the amide-aromatic hydrogen bond between Ala32 and Trp69 remains intact. This is the first example of tryptophan mediated photoreduction of a disulfide bond in proteins.     

Integration of production and aqueous two-phase systems extraction of extracellular Fusarium solani pisi cutinase fusion proteins

Genetic engineering was integrated with the production and purification of Fusarium solani pisi cutinases, in order to obtain the highest amount of enzyme activity units, after purification. An aqueous two-phase system (ATPS) of polyethylene glycol 3350, dipotassium phosphate and whole broth was used for the extraction of three extracellular cutinases expressed in Saccharomyces cerevisiae. The production/extraction process was evaluated regarding cutinases secretion in the medium, partition behaviour and extraction yields in the ATPS. The proteins studied were cutinase wild type and two fusion proteins of cutinase with the tryptophane-proline (WP) fusion tags, namely (WP)(2) and (WP)(4). The (WP)(4) fusion protein enabled a 300-fold increase of the cutinase partition coefficient when comparing to the wild type. However, the secretion of the fusion proteins was lower than of the wild type cutinase secretion. A batch extraction strategy was compared with a continuous extraction in a perforated rotating disc contactor (PRDC). The batch and continuous systems were loaded with as much as 60% (w/w) whole cultivation broth. The continuous extraction strategy provided a 2.5 higher separation capacity than the batch extraction strategy. Considering the integrated process, the cutinase-(WP)(2) proved to lead to the highest product activity, enabling five and six times more product activity than the wild type and the (WP)(4) fusion proteins, respectively.     

Genetic engineering of the Fusarium solani pisi lipase cutinase for enhanced partitioning in PEG-phosphate aqueous two-phase systems

The Fusarium solani pisi lipase cutinase has been genetically engineered to investigate the influence of C-terminal peptide extensions on the partitioning of the enzyme in PEG-salt based aqueous two-phase bioseparation systems. Seven different cutinase lipase variants were constructed containing various C-terminal peptide extensions including tryptophan rich peptide tags ((WP)(2) and (WP)(4)), positively ((RP)(4)) and negatively ((DP)(4)) charged tags as well as combined tags with tryptophan together with either positively ((WPR)(4)) or negatively ((WPD)(4)) charged amino acids. The modified cutinase variants were stably produced in Escherichia coli as secreted to the periplasm from which they were efficiently purified by IgG-affinity chromatography employing an introduced N-terminal IgG-binding ZZ affinity fusion partner present in all variants. Partitioning experiments performed in a PEG 4000/sodium phosphate aqueous two-phase system showed that for variants containing either (WP)(2) or (WP)(4) peptide extensions, 10- to 70-fold increases in the partitioning to the PEG rich top-phase were obtained, when compared to the wild type enzyme. An increased partitioning was also seen for cutinase variants tagged with both tryptophans and charged amino acids, whereas the effect of solely charged peptide extensions was relatively small. In addition, when performing partitioning experiments from cell disintegrates, the (WP)(4)-tagged cutinase showed a similarly high PEG-phase partitioning, indicating that the effect from the peptide tag was unaffected by the background of the host proteins. Taken together, the results show that the partitioning of the recombinantly produced cutinase model enzyme could be significantly improved by relatively minor genetic engineering and that the effects observed for purified proteins are retained also in an authentic whole cell disintegrate system. The results presented should be of general interest also for the improvement of the partitioning properties of other industrially interesting proteins including bulk enzymes.     

Backbone dynamics of Fusarium solani pisi cutinase probed by nuclear magnetic resonance: the lack of interfacial activation revisited

The backbone dynamics of Fusarium solani pisi cutinase has been studied by a variety of nuclear magnetic resonance experiments to probe internal motions on different time scales. The core of cutinase appears to be highly rigid. The binding site, including the oxyanion hole, is mobile on the microsecond to millisecond time scale, in contrast to the well-defined active site and preformed oxyanion hole elucidated by X-ray crystallography [Martinez, C., de Geus, P., Lauwereys, M., Matthyssens, G., and Cambillau, C. (1992) Nature 356, 615-618]. In this crystal structure, cutinase has a rather open conformation, in which the hydrophobic binding site is exposed. The observed mobility in solution most likely represents the interconversion between open and more closed conformations, like in a true lipase. The opening and closing motions are on a time scale which corresponds with the kinetics of the hydrolysis reaction, i.e., the millisecond range, which suggests that these conformational rearrangements form the rate-limiting step in catalysis. We conclude that the crystal structure probably represents one of the multiple conformations present in solution, which fortuitously is the active conformation. The implications of our findings are discussed with particular reference to the explanation of the lack of interfacial activation as found for cutinase.     

Hydrolysis of plant cuticle by plant pathogens. Properties of cutinase I, cutinase II, and a nonspecific esterase isolated from Fusarium solani pisi.

The properties of the homogeneous cutinase I, cutinase II, and the nonspecific esterase isolated from the extracellular fluid of cutin-grown Fusarium solani F. pisi (R.E. Purdy and P.E. Kolattukudy (1975), Biochemistry, preceding paper in this issue) were investigated. Using tritiated apple cutin as substrate, the two cutinases showed similar substrate concentration dependence, protein concentration dependence, time course profiles, and pH dependence profiles with optimum near 10.0. Using unlabeled cutin, the rate of dihydroxyhexadecanoic acid release from apple fruit cutin by cutinase I was determined to be 4.4 mumol per min per mg. The cutinases hydrolyzed methyl hexadecanoate, cyclohexyl hexadecanoate, and to a much lesser extent hexadecyl hexadecanoate but not 9-hexadecanoyloxyheptadecane, cholesteryl hexadecanoate, or hexadecyl cinnamate. The extent of hydrolysis of these model substrates by cutinase I was at least three times that by cutinase II. The nonspecific esterase hydrolyzed all of the above esters except hexadecyl cinnamate, and did so to a much greater extent than did the cutinases. None of the enzymes hydrolyzed alpha- or beta-glucosides of p-nitrophenol. p-Nitrophenyl esters of fatty acids from C2 through C18 were used as substrates and V's and Kms were determined...     

The effect of pre- and pro-sequences and multicopy integration on heterologous expression of the Fusarium solani pisi cutinase gene in Aspergillus awamori

 A synthetic derivative of the cutinase cDNA of Fusarium solani pisi was expressed in Aspergillus awamori using the A. awamori endoxylanase II (exlA) promoter and terminator. The influence of the origin of the pre-sequence and the presence of a pro-sequence on the efficiency of extracellular cutinase production was analysed in single-copy transformants containing an expression cassette integrated at the pyrG locus. Transformants containing a construct encoding a direct, in-frame fusion of the xylanase pre-peptide to the mature cutinase showed a 2-fold higher cutinase production level compared to strains containing constructs with an additional cutinase pro-peptide. The effect of multicopy integration of the expression cassette on cutinase production was analysed in strains with different numbers of a cutinase construct containing its own pre-prosequence. The multicopy strains showed a 6- to 12-fold increased production of extracellular cutinase relative to the single-copy strains. No linear dose response relation to the number of expression cassettes present in the strains was observed. The amount of active enzyme produced by the strains correlated with the amount of cutinase-specific mRNA, suggesting that cutinase overproduction is not limited at the level of translation or secretion. Received: 3 August 1995/Received revision: 20 December 1995/Accepted: 8 January 1996     

Isolation and characterization of a cutinase from Fusarium roseum culmorum and its immunological comparison with cutinases from F. solani pisi.

Fusarium roseum culmorum, grown on apple cutin as the sole source of carbon, was shown to produce a cutin depolymerizing enzyme. From the extracellular fluid of these F. roseum cultures, a cutinase and a nonspecific esterase were isolated utilizing Sephadex G-100, QAE-Sephadex, and SP-Sephadex chromatography. The homogeneity of the cutinase was verified by polyacrylamide disc gel electrophoresis. The molecular weight of the cutinase was estimated to be 24,300 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Electrophoretic mobility of this enzyme was between that of Cutinases I and II from Fusarium solani pisi. The F. roseum cutinase hydrolyzed p-nitrophenyl butyrate and cutin, but not p-nitrophenyl palmitate, while the nonspecific esterase hydrolyzed the long-chain esters. Amino acid composition of F. roseum cutinase was found to be similar to that of F. solani pisi Cutinase I except for differences in the number of serine, valine, and cysteine residues. The time-course, protein concentration dependence, substrate concentration dependence, and pH optimum (10.0 for cutin hydrolysis) of the F. roseum cutinase was similar to the cutinases from F. solani pisi. The F. roseum cutinase was inhibited by diisopropylfluorophosphate and paraoxon, and the [³H]diisopropylphosphate group was covalently attached to the enzyme upon treatment with tritiated diisopropylfluorophosphate. Therefore, it is concluded that catalysis by cutinase involves an “active serine.” Immunochemical studies with a rabbit antibody prepared against F. solani pisi Cutinase I demonstrated that Cutinase II from this organism was immunologically very similar to, but not identical to, Cutinase I. On the other hand, the cutinase from F. roseum was immunologically quite different from the cutinases isolated from F. solani pisi in that it did not cross-react with anticutinase I. However, all three cutinases were virtually identical in their sensitivity to inhibition by anticutinase I, and all three enzymes were virtually completely inhibited by the anticutinase I.     

De novo design, synthesis and screening of a combinatorial library of complementary ligands directed towards the surface of cutinase from Fusarium solani pisi

The protein surface is the interface through which a protein molecule senses the external world. The composition of this interface, in charged, polar and/or hydrophobic residues is crucial for both the activity and stability of the protein. Protein immobilization on surfaces has been extensively explored as one of the most effective approaches for stabilization. The mechanism of stabilization, however, is still poorly understood, and usually the success of any method is more a matter of trial and error rather than the result of rational concepts. The importance of local unfolding processes in a number of biologically significant processes has been recognized and attracted increasing attention. Unfolding regions have been localized in different proteins including the recombinant cutinase from Fusarium solani pisi. The study of three structural surface regions associated with early cutinase unfolding events was the basis for the approach followed in this work. A 64-member solid-phase combinatorial library of ligands was synthesized on a triazine-substituted agarose matrix using a modified 'mix and split' procedure. The combinatorial library was assessed for binding to cutinase from Fusarium solani pisi in a biologically active form. Four lead ligands (3/5, 3/7, 4/5, 4/7) have been selected in which immobilized cutinase presented a relative activity of 30-60% as compared to the free enzyme.     

Improved stability and reactivity of Fusarium solani cutinase in supercritical CO2

Cutinase from Fusarium solani pisi was immobilized on Accurel EP100 and catalyzed the esterification of hexanoic acid with hexanol in supercritical CO. The enzyme lost only 10% of its activity over six days. Esterification was maximal with a water activity of a = 0.76.     

1H, 13C, and 15N resonance assignments of Fusarium solani pisi cutinase and preliminary features of the structure in solution.

Essentially complete (96%) sequence-specific assignments were made for the backbone and side-chain 1H, 13C, and 15N resonances of Fusarium solani pisi cutinase, produced as a 214-residue heterologous protein in Escherichia coli, using heteronuclear NMR techniques. Three structural features were noticed during the assignment. (1) The secondary structure in solution corresponds mostly with the structure from X-ray diffraction, suggesting that both structures are globally similar. (2) The HN of Ala32 has a strongly upfield-shifted resonance at 3.97 ppm, indicative of an amide-aromatic hydrogen bond to the indole ring of Trp69 that stabilizes the N-terminal side of the parallel beta-sheet. (3) The NMR data suggest that the residues constituting the oxyanion hole are quite mobile in the free enzyme in solution, in contrast to the existence of a preformed oxyanion hole as observed in the crystal structure. Apparently, cutinase forms its oxyanion hole upon binding of the substrate like true lipases.