The gene encoding a cutinase homolog, LC-cutinase, was cloned from a fosmid library of a leaf-branch compost metagenome by functional screening using tributyrin agar plates. LC-cutinase shows the highest amino acid sequence identity of 59.7% to Thermomonospora curvata lipase. It also shows the 57.4% identity to Thermobifida fusca cutinase. When LCcutinase without a putative signal peptide was secreted to the periplasm of Escherichia coli cells with the assistance of the pelB leader sequence, more than 50% of the recombinant protein, termed LC-cutinase*, was excreted into the extracellular medium. It was purified and characterized. LC-cutinase* hydrolyzed various fatty acid monoesters with acyl chain lengths of 2 to 18, with a preference for short-chain substrates (C 4 substrate at most) most optimally at pH 8.5 and 50°C, but could not hydrolyze olive oil. It lost activity with half-lives of 40 min at 70°C and 7 min at 80°C. LC-cutinase* had an ability to degrade poly(-caprolactone) and polyethylene terephthalate (PET). The specific PET-degrading activity of LC-cutinase* was determined to be 12 mg/h/mg of enzyme (2.7 mg/h/kat of pNP-butyrate-degrading activity) at pH 8.0 and 50°C. This activity is higher than those of the bacterial and fungal cutinases reported thus far, suggesting that LC-cutinase* not only serves as a good model for understanding the molecular mechanism of PET-degrading enzyme but also is potentially applicable for surface modification and degradation of PET. C utinase (EC 3.1.1.74) is a lipolytic/esterolytic enzyme that hydrolyzes not only cutin, which is a major component of plant cuticle (38), but also water-soluble esters and insoluble triglycerides (12). It hydrolyzes these substrates to carboxylic acids and alcohols through the formation of an acyl enzyme intermediate, in which the active-site serine residue is acylated by the substrate. This serine residue is located within a GXSXG sequence motif and forms a catalytic triad with His and Asp. Cutinase has been found in both fungi and bacteria. The crystal structures of two fungal cutinases from Fusarium solani f. sp. pisi (22) and Glomerella cingulata (27) have been determined. According to these structures, cutinase shares a common ␣/␤ hydrolase fold with lipase and esterase (28). However, cutinase, like esterase, does not have a lid structure, which is responsible for interfacial activation of lipase (8). Therefore, cutinase does not show interfacial activation like esterase (14). Cutinase has recently received much attention because of its potential application for surface modification and degradation of aliphatic and aromatic polyesters (16), especially polyethylene terephthalate (PET), which is a synthetic aromatic polyester composed of terephthalic acid (TPA) and ethylene glycol (10,16,36,39). However, the number of cutinases, which have been studied regarding PET modification, is still limited, and this limitation may result in the delay of the research toward the practical use of cutinases. Therefore, isolation of a novel cutinase...

The crystal structure of metagenome-derived LC-cutinase with polyethylene terephthalate (PET)-degrading activity was determined at 1.5 Å resolution. The structure strongly resembles that of Thermobifida alba cutinase. Ser165, Asp210, and His242 form the catalytic triad. Thermal denaturation and guanidine hydrochloride (GdnHCl)-induced unfolding of LC-cutinase were analyzed at pH 8.0 by circular dichroism spectroscopy. The midpoint of the transition of the thermal denaturation curve, T1/2, and that of the GdnHCl-induced unfolding curve, Cm, at 30 °C were 86.2 °C and 4.02 M, respectively. The free energy change of unfolding in the absence of GdnHCl, ΔG(H2O), was 41.8 kJ mol(-1) at 30 °C. LC-cutinase unfolded very slowly in GdnHCl with an unfolding rate, ku(H2O), of 3.28 × 10(-6) s(-1) at 50 °C. These results indicate that LC-cutinase is a kinetically robust protein. Nevertheless, the optimal temperature for the activity of LC-cutinase toward p-nitrophenyl butyrate (50 °C) was considerably lower than the T1/2 value. It increased by 10 °C in the presence of 1% polyethylene glycol (PEG) 1000. It also increased by at least 20 °C when PET was used as a substrate. These results suggest that the active site is protected from a heat-induced local conformational change by binding of PEG or PET. LC-cutinase contains one disulfide bond between Cys275 and Cys292. To examine whether this disulfide bond contributes to the thermodynamic and kinetic stability of LC-cutinase, C275/292A-cutinase without this disulfide bond was constructed. Thermal denaturation studies and equilibrium and kinetic studies of the GdnHCl-induced unfolding of C275/292A-cutinase indicate that this disulfide bond contributes not only to the thermodynamic stability but also to the kinetic stability of LC-cutinase.

Transcripts from mitochondrial and chloroplast DNA of land plants often undergo cytidine to uridine conversion-type RNA editing events. RESOPS is a newly built database that specializes in displaying RNA editing sites of land plant organelles on protein three-dimensional (3D) structures to help elucidate the mechanisms of RNA editing for gene expression regulation. RESOPS contains the following information: unedited and edited cDNA sequences with notes for the target nucleotides of RNA editing, conceptual translation from the edited cDNA sequence in pseudo-UniProt format, a list of proteins under the influence of RNA editing, multiple amino acid sequence alignments of edited proteins, the location of amino acid residues coded by codons under the influence of RNA editing in protein 3D structures and the statistics of biased distributions of the edited residues with respect to protein structures. Most of the data processing procedures are automated; hence, it is easy to keep abreast of updated genome and protein 3D structural data. In the RESOPS database, we clarified that the locations of residues switched by RNA editing are significantly biased to protein structural cores. The integration of different types of data in the database also help advance the understanding of RNA editing mechanisms. RESOPS is accessible at http://cib.cf.ocha.ac.jp/RNAEDITING/.

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Aims:The methylotrophic yeast Pichia pastoris is widely used to express foreign proteins fused to secretion signals. As the effect of the expression host on the final protein product is unclear, we compared the properties of an endoglucanase (eglB of Aspergillus niger) expressed in two different P. pastoris strains. Methodology and results: Full-length cDNA encoding endoglucanase of A. niger strain ATCC10574 was isolated and expressed in P. pastoris X33 (the methanol utilisation plus phenotype, Mut + ) and P. pastoris GS115 (slow methanol utilisation, Mut S ). EglB-GS115 showed the highest activity and stability at 60 °C while EglB-X33 was most active at 50 °C. EglB-X33 was active towards other substrates such as arabinogalactan, guar gum and locust bean gum besides its specific substrate, carboxymethyl cellulose (CMC). However, EglB-GS115 was only active on CMC. The affinity of EglB-X33 towards CMC (Km = 7.5 mg/mL and specific activity 658 U/mg) was higher than that of EglB-GS115 (Km = 11.57 mg/mL, specific activity 144 U/mg). Conclusion, significance and impact of study: Although eglB was cloned in the same expression vector (pPICZαC), two different characteristics of enzymes were recovered from the supernatant of the different hosts. Thus, expression of recombinant enzyme in different P. pastoris strains greatly affects the physical structure and biochemical properties of the enzyme.