Currently Available Recombinant Alternatives to Horseshoe Crab Blood Lysates: Are They Comparable for the Detection of Environmental Bacterial Endotoxins? A Review.

Endotoxin testing by recombinant factor C (rFC) is increasing with the addition of new suppliers of reagents. By use of a recombinantly produced factor C , based on the sequence of a coagulation enzyme present in horseshoe crab amebocyte lysates, the rFC tests are designed as substitutes for the traditional Limulus amebocyte lysate (LAL)/Tachypleus amebocyte lysate tests based on horseshoe crab blood. Comparative testing of samples with both the LAL and recombinant reagents has shown a high degree of correlation, suggesting that use of rFC is comparable to the more traditional LAL tests and may be technologically superior. Recombinant factor C does not recognize the factor G pathway, the alternate coagulation pathway that the lysate reagents detect. This feature allows rFC to detect endotoxin more selectively. As a recombinantly produced material, it avoids the use of the horseshoe crabs required for lysate production, thereby protecting this species, which is at risk in some parts of the world. Recombinant factor C is expected to further benefit from a more sustainable supply chain based upon a robust biotechnological production process. We summarize here the results of many studies that evaluated the use of recombinant technology for the detection of environmental endotoxin. Additionally, we include a review of the current compendia and regulatory status of the recombinant technologies for use in the quality control of pharmaceutical manufacturing. Our analysis confirms that the recombinant technologies are comparable in protecting patient safety.

Mimicking cotranslational folding of prosubtilisin E in vitro.

Nascent polypeptides are synthesized on ribosomes starting at the N-terminus and simultaneously begin to fold during translation. We constructed N-terminal fragments of prosubtilisin E containing an intramolecular chaperone (IMC) at N-terminus to mimic cotranslational folding intermediates of prosubtilisin. The IMC-fragments of prosubtilisin exhibited progressive enhancement of their secondary structures and thermostabilities with increasing polypeptide length. However, even the largest IMC-fragment with 72 residues truncated from the C-terminus behaved as a molten globule, indicating the requirement of the C-terminal region to have a stable tertiary structure. Furthermore, truncation of the IMC in the IMC-fragments resulted in aggregation, suggesting that the IMC plays a crucial role to prevent misfolding and aggregation of cotranslational folding intermediates during translation of prosubtilisin polypeptide.

Production and characterization of collagenase from a new Amazonian Bacillus cereus strain.

A new collagenase producing a strain of Bacillus cereus, isolated from the pollen of a bee of Amazon Region (Brazil), had its enzyme characterized and the production medium composition and culture conditions enhanced. A two-level design on three factors, namely initial medium pH, the substrate (gelatin) concentration and agitation intensity, allowed identifying the first two variables as the most significant ones, while a central composite design (CCD) was subsequently used to identify their optimal levels. Statistics highlighted maximized collagenolytic activity when substrate concentration and initial medium pH were selected at their highest levels (positive effects), whereas agitation intensity at the lowest (negative effect). Triplicate runs performed under predicted optimal conditions (pH 7.8 and 1.7% gelatin concentration) yielded a collagenolytic activity (305.39 ± 5.15 U) 4.6- to 15-fold those obtained with the preliminary design. The enzyme displayed optimum activity at 45 °C and pH 7.2, was stable over wide ranges of pH values and temperatures (7.2-11.0 and 25-50 °C, respectively) and was strongly inhibited by 10 mM phenylmethylsulphonyl fluoride. The zymogram showed two prominent bands at 50 and 76 kDa. These results are a first attempt to elucidate the features of this new collagenase, its production conditions, and possible scale-up.

An Ancestral Tryptophanyl-tRNA Synthetase Precursor Achieves High Catalytic Rate Enhancement without Ordered Ground-State Tertiary Structures.

Urzymes-short, active core modules derived from enzyme superfamilies-prepared from the two aminoacyl-tRNA synthetase (aaRS) classes contain only the modules shared by all related family members. They have been described as models for ancestral forms. Understanding them currently depends on inferences drawn from the crystal structures of the full-length enzymes. As aaRS Urzymes lack much of the mass of modern aaRS's, retaining only a small portion of the hydrophobic cores of the full-length enzymes, it is desirable to characterize their structures. We report preliminary characterization of (15)N tryptophanyl-tRNA synthetase Urzyme by heteronuclear single quantum coherence (HSQC) NMR spectroscopy supplemented by circular dichroism, thermal melting, and induced fluorescence of bound dye. The limited dispersion of (1)H chemical shifts (0.5 ppm) is inconsistent with a narrow ensemble of well-packed structures in either free or substrate-bound forms, although the number of resonances from the bound state increases, indicating a modest, ligand-dependent gain in structure. Circular dichroism spectroscopy shows the presence of helices and evidence of cold denaturation, and all ligation states induce Sypro Orange fluorescence at ambient temperatures. Although the term "molten globule" is difficult to define precisely, these characteristics are consistent with most such definitions. Active-site titration shows that a majority of molecules retain ∼60% of the transition state stabilization free energy observed in modern synthetases. In contrast to the conventional view that enzymes require stable tertiary structures, we conclude that a highly flexible ground-state ensemble can nevertheless bind tightly to the transition state for amino acid activation.

Immune indices and identical functions of two prophenoloxidases from the haemolymph of green tiger shrimp Penaeus semisulcatus and its antibiofilm activity.

In the present study, we purified two prophenoloxidases (proPO) from haemolymph of green tiger shrimp, Penaeus semisulcatus by gel fermentation chromatography using blue Sepharose matrix. The two purified prophenoloxidase macromolecules are of about 76 and 75 kDa determined through SDS-PAGE and named as Penaeus semisulcatus prophenoloxidase I (PSproPO I) and Penaeus semisulcatus prophenoloxidase II (PSproPO II). It was further characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Circular Dichroism (CD) and High Performance Liquid Chromatography (HPLC) analysis. The purified PSproPO I and PSproPO II showed the strongest agglutination titre against human erythrocytes compared to goat RBC. The PSproPO I and PSproPO II showed phagocytic activity against yeast Saccharomyces cerevisiae and encapsulation activity against Sepharose CL 6B beads compared to CM Sepharose and Sodium alginate beads. The functional analysis of purified PSproPO I and PSproPO II showed enhanced PO activity when added with the triggering molecules such as pathogen associated molecular patterns (PAMPs), metals and chemicals. In addition, eluted fraction containing PSproPO I and PSproPO II showed antibiofilm activity against Gram positive and Gram negative bacteria. The above results concluded that no significant differences were found between the purified PSproPO I and PSproPO II immune indices and functions. This study might provide a sensitive platform to understand more about the critical roles of PSproPO I and PSproPO II in crustacean immune system.

Cross-talk between NADPH oxidase-PKCα-p(38)MAPK and NF-κB-MT1MMP in activating proMMP-2 by ET-1 in pulmonary artery smooth muscle cells.

Treatment of bovine pulmonary artery smooth muscle cells with endothelin-1 (ET-1) caused an increase in the expression and activation of proMMP-2 in the cells. The present study was undertaken to determine the underlying mechanisms involved in this scenario. We demonstrated that (i) pretreatment with NADPH oxidase inhibitor, apocynin; PKC-α inhibitor, Go6976; p(38)MAPK inhibitor SB203580 and NF-κB inhibitor, Bay11-7082 inhibited the expression and activation of proMMP-2 induced by ET-1; (ii) ET-1 treatment to the cells stimulated NADPH oxidase and PKCα activity, p(38)MAPK phosphorylation as well as NF-κB activation by translocation of NF-κBp65 subunit from cytosol to the nucleus, and subsequently by increasing its DNA-binding activity; (iii) ET-1 increases MT1-MMP expression, which was inhibited upon pretreatment with apocynin, Go6976, SB293580, and Bay 11-7082; (iv) ET-1 treatment to the cells downregulated TIMP-2 level. Although apocynin and Go6976 pretreatment reversed ET-1 effect on TIMP-2 level, yet pretreatment of the cells with SB203580 and Bay 11-7082 did not show any discernible change in TIMP-2 level by ET-1. Overall, our results suggest that ET-1-induced activation of proMMP-2 is mediated via cross-talk between NADPH oxidase-PKCα-p(38)MAPK and NFκB-MT1MMP signaling pathways along with a marked decrease in TIMP-2 expression in the cells.

Purification and molecular cloning of aspartic proteinases from the stomach of adult Japanese fire belly newts, Cynops pyrrhogaster.

Six aspartic proteinase precursors, a pro-cathepsin E (ProCatE) and five pepsinogens (Pgs), were purified from the stomach of adult newts (Cynops pyrrhogaster). On sodium dodecylsulfate-polyacrylamide gel electrophoresis, the molecular weights of the Pgs and active enzymes were 37-38 kDa and 31-34 kDa, respectively. The purified ProCatE was a dimer whose subunits were connected by a disulphide bond. cDNA cloning by polymerase chain reaction and subsequent phylogenetic analysis revealed that three of the purified Pgs were classified as PgA and the remaining two were classified as PgBC belonging to C-type Pg. Our results suggest that PgBC is one of the major constituents of acid protease in the urodele stomach. We hypothesize that PgBC is an amphibian-specific Pg that diverged during its evolutional lineage. PgBC was purified and characterized for the first time. The purified urodele pepsin A was completely inhibited by equal molar units of pepstatin A. Conversely, the urodele pepsin BC had low sensitivity to pepstatin A. In acidic condition, the activation rates of newt pepsin A and BC were similar to those of mammalian pepsin A and C1, respectively. Our results suggest that the enzymological characters that distinguish A- and C-type pepsins appear to be conserved in mammals and amphibians.

Production of soluble and active microbial transglutaminase in Escherichia coli for site-specific antibody drug conjugation.

Applications of microbial transglutaminase (mTGase) produced from Streptomyces mobarensis (S. mobarensis) were recently extended from food to pharmaceutical industry. To use mTGase for clinical applications, like generation of site specific antibody drug conjugates, it would be beneficial to manufacture mTGase in Escherichia coli (E. coli). To date, attempts to express recombinant soluble and active S. mobarensis mTGase have been largely unsuccessful. mTGase from S. mobarensis is naturally expressed as proenzyme and stepwise proteolytically processed into its active mature form outside of the bacterial cell. The pro-domain is essential for correct folding of mTGase as well as for inhibiting activity of mTGase inside the cell. Here, we report a genetically modified mTGase that has full activity and can be expressed at high yields in the cytoplasm of E. coli. To achieve this we performed an alanine-scan of the mTGase pro-domain and identified mutants that maintain its chaperone function but destabilize the cleaved pro-domain/mTGase interaction in a temperature dependent fashion. This allows proper folding of mTGase and keeps the enzyme inactive during expression at 20°C, but results in full activity when shifted to 37°C due to loosen domain interactions. The insertion of the 3C protease cleavage site together with pro-domain alanine mutants Tyr14, Ile24, or Asn25 facilitate high yields (30-75 mg/L), and produced an enzyme with activity identical to wild type mTGase from S. mobarensis. Site-specific antibody drug conjugates made with the E .coli produced mTGase demonstrated identical potency in an in vitro cell assay to those made with mTGase from S. mobarensis.

Expression, purification and auto-activation of cathepsin E from insect cells.

Cathepsin E is an aspartic protease that belongs to the pepsin family. This protease is similar to cathepsin D but differs in its tissue distribution and cell localization. Elevated levels of this enzyme are linked to several tumors, including devastating pancreatic ductal adenocarcinoma. In this manuscript, we present a new protocol for the high-yield purification of recombinant human cathepsin E in the baculovirus expression system. The recombinant protein was produced by the Sf9 insect cell line and secreted into the medium in the form of an inactive zymogen. Procathepsin E was purified using ion-exchange and size exclusion chromatographies followed by pepstatin- and heparin-affinity chromatography steps. The zymogen was activated at an acidic pH, resulting in a high yield of the activated intermediate of cathepsin E. The enzymatic activity, stability, and molecular weight corresponded to those of cathepsin E. The new purification procedure will promote further studies of this enzyme to improve the understanding of its structure-function relationship and consequently enable the development of better therapeutic approaches.

Listeriosis en México: importancia clínica y epidemiológica / Listeriosis in Mexico: Clinical and epidemiological importance

La listeriosis es una enfermedad transmitida por alimentos (ETA) y ocasionada por Listeria monocytogenes. La importancia de ésta se debe a su impacto clínico, la alta tasa de mortalidad y el efecto económico derivado de los brotes asociados con el consumo de alimentos. En México, las fallas en los sistemas de vigilancia epidemiológicos son causa de información imprecisa sobre la incidencia de la listeriosis y sobre su caracterización como ETA. En este trabajo se presentan datos referentes a la presencia de la bacteria en alimentos, reportes de casos de la enfermedad y patologías relacionadas con infección por L. monocytogenes. La falta de datos exactos sobre la importancia de esta bacteria plantea la necesidad de concientizar a las instancias correspondientes para definir estrategias de búsqueda intencionada de L. monocytogenes en alimentos y de la recopilación de información clínica precisa que permita conocer la importancia clínica y epidemiológica de la listeriosis en México.

Listeriosis is caused by Listeria monocytogenes, an important food-borne disease due to its clinical forms, high mortality rate, and the economic impact in both clinical and food production industries. In Mexico, the lack of epidemiological surveillance systems leads to the need of accurate data on the incidence of listeriosis and its association with food-borne disease. In this paper, we present data about the presence of this bacterium in food, reports related to clinical cases of listeriosis, and information of diseases in which L. monocytogenes may be involved. However, in most of these cases the etiology was not established. Given this, there's a need to inform and warn the appropriate entities, to define strategies for the mandatory search of L. monocytogenes through the whole food production chain and clinical suspects, for the epidemiological importance and control of listeriosis in Mexico.

Lysozyme and defense peptides as suppressors of phenoloxidase activity in Galleria mellonella.

The prophenoloxidase (proPO) cascade supplies quinones and other reactive compounds for melanin formation, protein cross-linking, hemolymph coagulation, and killing of microbial invaders as well as parasites. The high cytotoxicity of the generated compounds requires a strict control of the activation of the proPO system and phenoloxidase (PO) activity to minimize damage to host tissues and cells. The PO activity in hemolymph of Escherichia coli challenged Galleria mellonella larvae increased, with a temporal drop 1 h after the challenge, reaching the highest level 24 h after the challenge. In the present study, a potential role of G. mellonella defense peptides and lysozyme in controlling the proPO system was investigated. The effects of purified defense peptides (anionic peptides 1 and 2, cecropin D-like peptide, Galleria defensin, proline-rich peptides 1 and 2) and lysozyme were analyzed. Four compounds, namely lysozyme, Galleria defensin, proline-rich peptide 1, and anionic peptide 2, decreased the hemolymph PO activity considerably, whereas the others did not affect the enzyme activity level. Our results indicate that these hemolymph factors could play multiple and distinct roles in the insect immune response.

Optimized expression, purification and characterization of a family 11 xylanase (AuXyn11A) from Aspergillus usamii E001 in Pichia pastoris.

BACKGROUND: Xylanases have attracted much attention because of their potential applications. Unfortunately, the commercialization of xylanases is limited by their low catalytic activities. The aim of this study was to improve the activity of a xylanase by optimization of the expression conditions and to investigate its characterization. RESULTS: The activity of recombinant AuXyn11A (reAuXyn11A), a family 11 xylanase from Aspergillus usamii E001 expressed in Pichia pastoris GS115, reached 912.6 U mL⁻¹ under the optimized conditions, which was 2.14 times as high as that expressed using the standard protocol. After the endogenous 18-aa propeptide had been processed in P. pastoris, reAuXyn11A (188-aa mature peptide) was secreted and purified with a specific activity of 22 714 U mg⁻¹. It displayed maximum activity at pH 5 and 50 °C and was stable in the pH range 4-8 and at a temperature of 45 °C or below. Its activity was not significantly affected by most metal ions and EDTA. Xylooligosaccharides ranging from xylobiose (X2) to xylohexaose (X6) were produced from insoluble corncob xylan by reAuXyn11A. CONCLUSION: Its high specific activity and good enzymatic properties suggest that reAuXyn11A is a potential candidate for applications in industrial processes.

A novel prophenoloxidase, hemocyanin encoded copper containing active enzyme from prawn: gene characterization.

The copper containing prophenoloxidase enzyme plays a crucial role in the defense system of arthropods, especially crustaceans and insects. In this study, we have reported a full length cDNA of prophenoloxidase identified from the constructed cDNA library of freshwater prawn Macrobrachium rosenbergii by genome sequence FLX technology. The identified full length M. rosenbergii prophenoloxidase (MrProPO) consists of 3378 base pairs (bp) with an open reading frame (ORF) of 2099 bp. This ORF encoded a polypeptide of 700 amino acids (aa) with an estimated molecular mass of 80 kDa and a predicted isoelectric point (pI) of 6.7. The motif analysis of MrProPO shows two copper binding sites (CuA and CuB) along with hemocyanin signatures and a thiol-ester like motif. MrProPO exhibited the maximum similarity (97%) with ProPO from Macrobrachium nipponense and is closely clustered with other crustacean ProPO in the phylogenetic tree. Bioinformatics analysis suggests that MrProPO is a member of the prophenoloxidase family, due to the conserved domains, motifs and similarity with other known ProPOs. The 3D structural analysis of MrProPO reveals that it has more random coils, moderate α-helices, few extended ß-sheets and a very few ß-turns. Among the 700 aa of MrProPO, 355 (50.71%), 206 (29.43%), 110 (15.71%) and 29 (4.14%) amino acids are responsible for random coils, α-helices, extended ß-sheets and ß-turns respectively. The gene expression results indicate MrProPO is widely distributed in all the tissues studied, but significantly (P<0.05) highest expression was observed in hepatopancreas. The relative expression of mRNA was quantified in hepatopancreas after being infected with virus [white spot syndrome baculovirus (WSBV) and M. rosenbergii nodovirus (MrNV)] and bacteria (Aeromonas hydrophila and Vibrio harveyi) using real-time PCR. MrProPO mRNA transcription significantly (P<0.05) increased at 24h post injection (p.i.) with subsequent decrease at 48 h p.i. in both viral and bacterial infected prawns. The highest enzyme activity was observed in hepatopancreas, which was also significantly higher (P<0.05) than detected in other tissues. Similar to gene expression results, the enzyme activity reached the peak at 24h p.i. and then the activity started decreasing. Overall results indicate that MrProPO is very likely to participate in the acute response against pathogen entry in prawns.

Recombinant expression of the autocatalytic complement protease MASP-1 is crucially dependent on co-expression with its inhibitor, C1 inhibitor.

MASP-1 is a protease of the lectin pathway of complement. It is homologous with MASP-2, previously thought both necessary and sufficient for lectin pathway activation. Recently MASP-1 has taken centre stage with the observation that it is crucial to the activation of MASP-2 and thus central to complement activation. Numerous additional functions have been suggested for MASP-1 and its importance is obvious. Yet, thorough analyses of proteolytic activities and physiological roles in the human scenario have been hampered by difficulties in purifying or producing full-length human MASP-1. We present the successful expression of full-length recombinant human MASP-1 entirely in the zymogen form in a mammalian expression system. We found that the catalytic activity of MASP-1 suppresses its expression through rapid auto-activation and auto-degradation. This auto-degradation was not inhibited by the addition of inhibitors to the culture medium, and it was subsequently found to occur intracellularly. Numerous mutations aimed at attenuating auto-activation or preventing auto-degradation failed to rescue expression, as did also attempts at stabilizing the protease by co-expression with MBL or ficolins or expression in hepatocyte cell lines, representing the natural site of synthesis. The active protease was finally produced through co-expression with the serine protease inhibitor C1 inhibitor. We demonstrate that the expressed protease is capable of binding MBL and auto-activating, and is catalytically active. We have generalized the concept to the expression also of MASP-2 entirely in its zymogen form and with improved yields. We suggest a general advantage of expressing aggressive, autocatalytic proteases with their cognate inhibitors.

Constitutive expression, purification and characterization of bovine prochymosin in Pichia pastoris GS115.

Chymosin can specifically break down the Phe105-Met106 peptide bond of milk κ-casein to form insoluble para-κ-casein, resulting in milk coagulation, a process that is used in making cheese. In this study, in order to obtain an alternative milk coagulant which is safe and efficient, and simultaneously can produce cheese with a good taste, bovine prochymosin B was chosen and constitutively expressed to a high level in Pichia pastoris. The recombinant chymosin was expressed mainly as a secretory form, and it exhibited milk-clotting activity. It was purified by ammonium sulfate fractionation, anion exchange, followed by cation exchange chromatography. A final yield of 24.2% was obtained for the purified enzyme, which appeared as a single band in SDS-PAGE having a molecular mass of approximate 36 kDa. Proteolysis assay showed that it specifically hydrolyzed κ-casein. It was stable at 25-50°C and had optimal activity at 37°C and pH 4.0. The activity of the recombinant chymosin was activated by cations such as Mn(2+), Fe(3+), Mg(2+) and Na(+), but inhibited by K(+), Co(2+), Zn(2+), Ni(2+), and to a lesser extent by Cu(2+). These results suggested that recombinant bovine chymosin is an acid milk coagulant, and it could be considered as a safe and efficient enzyme suitable for use in cheese production.

Purification and characterization of prophenoloxidase from Galleria mellonella L.

Prophenoloxidase (PPO) was purified from Galleria mellonella L. A 67-fold purification of the proenzyme with 352% yield was achieved by using a Sepharose 4B-L-tyrosine-p-amino benzoic acid affinity column. The purified enzyme was migrated as a single band on SDS-polyacrylamide gel electrophoresis. K(m) and V(max) values were 0.017 M and 1430.45 EU for catechol. Inhibition of PPO was investigated with inhibitors such as p-aminobenzoic acid, etyleneglycol, and ascorbic acid. Among them, ascorbic acid showed the strongest inhibitory activity with IC(50) value of 2.94 µM. The current paper represents new strategies for the biological control of the Galleria mellonella L. insect.

The 3D structure and function of digestive cathepsin L-like proteinases of Tenebrio molitor larval midgut.

Cathepsin L-like proteinases (CAL) are major digestive proteinases in the beetle Tenebrio molitor. Procathepsin Ls 2 (pCAL2) and 3 (pCAL3) were expressed as recombinant proteins in Escherichia coli, purified and activated under acidic conditions. Immunoblot analyses of different T. molitor larval tissues demonstrated that a polyclonal antibody to pCAL3 recognized pCAL3 and cathepsin L 3 (CAL3) only in the anterior two-thirds of midgut tissue and midgut luminal contents of T. molitor larvae. Furthermore, immunocytolocalization data indicated that pCAL3 occurs in secretory vesicles and microvilli in anterior midgut. Therefore CAL3, like cathepsin L 2 (CAL2), is a digestive enzyme secreted by T. molitor anterior midgut. CAL3 hydrolyses Z-FR-MCA and Z-RR-MCA (typical cathepsin substrates), whereas CAL2 hydrolyses only Z-FR-MCA. Active site mutants (pCAL2C25S and pCAL3C26S) were constructed by replacing the catalytic cysteine with serine to prevent autocatalytic processing. Recombinant pCAL2 and pCAL3 mutants (pCAL2C25S and pCAL3C26S) were prepared, crystallized and their 3D structures determined at 1.85 and 2.1 Å, respectively. While the overall structure of these enzymes is similar to other members of the papain superfamily, structural differences in the S2 subsite explain their substrate specificities. The data also supported models for CAL trafficking to lysosomes and to secretory vesicles to be discharged into midgut contents.

Mass spectrometric characterization of human N-acylethanolamine-hydrolyzing acid amidase.

N-Acylethanolamine-hydrolyzing acid amidase (NAAA) is a lysosomal enzyme that primarily degrades palmitoylethanolamine (PEA), a lipid amide that inhibits inflammatory responses. We developed a HEK293 cell line stably expressing the NAAA pro-enzyme (zymogen) and a single step chromatographic purification of the protein from the media. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry MALDI-TOF MS analysis of the zymogen (47.7 kDa) treated with peptide-N-glycosidase F (PNGase F) identified 4 glycosylation sites, and acid cleavage of the zymogen into α- and ß-subunits (14.6 and 33.3 kDa) activated the enzyme. Size exclusion chromatography estimated the mass of the active enzyme as 45 ± 3 kDa, suggesting formation of an α/ß heterodimer. MALDI-TOF MS fingerprinting covered more than 80% of the amino acid sequence, including the N-terminal peptides, and evidence for the lack of a disulfide bond between subunits. The significance of the cysteine residues was established by their selective alkylation resulting in almost complete loss of activity. The purified enzyme was kinetically characterized with PEA and a novel fluorogenic substrate, N-(4-methyl coumarin) palmitamide (PAMCA). The production of sufficient quantities of NAAA and a high throughput assay could be useful in discovering novel inhibitors and determining the structure and function of this enzyme.

Serological diagnosis of clonorchiasis: using a recombinant propeptide of cathepsin L proteinase from Clonorchis sinensis as a candidate antigen.

Clonorchiasis is a common zoonosis in southern and northeastern parts of China, especially in Guangdong, Guangxi and Jilin province. Anti-Clonorchis sinensis antibody detection by enzyme-linked immunosorbent assay (ELISA) has been used for epidemiological surveys of clonorchiasis for its convenience and celerity, but it is still a meaningful work to screen ideal diagnostic antigen or antibody subtype for improvement of diagnostic sensitivity and specificity and for judgement of curative effect. In the present study, recombinant CsCatL-propeptide (rCsCatL-propeptide) was highly expressed in form of inclusion body in Escherichia coli. Soluble rCsCatL-propeptide with high purity were obtained after purification in denatured condition by using His Bind Purification kit, and then renatured. The major antibody subtypes responding to rCsCatL-propeptide in sera from clonorchiasis patients were IgG1 and IgG4, but the level of IgG4 was more predominant (P < 0.05). The sensitivity of specific IgG4 detection (91.7%) was statistically significantly higher than that of IgG1 (25.0%) with rCsCatL-propeptide (P < 0.01). The specificities of IgG1 and IgG4 detection with rCsCatL-propeptide were 83.3% and 88.5%, respectively, and the difference between them was not statistically significant (P > 0.05). Cross-reactions took place when we detected IgG1 of sera from patients infected with Schistosoma japonicum, Paragonimus westermani, hookworm, Trichuris trichiura and Ascaris lumbricoides with rCsCatL-propeptide, while cross-reactions only took place in sera from patients infected with S. japonicum and P. westermani when we detected specific IgG4. The positive rate of IgG4 detection in sera from clonorchiasis patients with <1,000, 1,000-4,999, 5,000-9,999, and ≥10,000 eggs per gram faeces (EPG) were 76.9%, 89.3%, 95.6%, and 100.0%, respectively. The positive rates of serodiagnosis correlated well with the EPG (r = 0.93). Overall, rCsCatL-propeptide is a valuable candidate for specific IgG4 detection in sera from clonorchiasis patients by the method of ELISA for its few cross-reaction and acceptable sensitivity. In addition, specific IgG4 detection can be used to valuate infected degree and therapeutic effect of clonorchiasis patients.

A novel type of prophenoloxidase from the kuruma prawn Marsupenaeus japonicus contributes to the melanization of plasma in crustaceans.

Melanization is one of the major immune responses in arthropods. Prophenoloxidases (proPOs) catalyze the oxidation of mono- or o-diphenols, a reaction that is the key initial step of melanin formation. Well-characterized proPOs from crustaceans are synthesized in haemocytes and are released into plasma in response to microbial attack. However, PO activity does exist in the plasma of haemolymph without pathogenic infections. Here, we demonstrate that a novel type of proPO contributes to such PO activity in the plasma fraction of haemolymph of crustaceans. The novel enzyme, which was purified from the plasma of the kuruma prawn (Marsupenaeus japonicus), possessed strong and specific monophenol and o-diphenol oxidation activity compared with that of known haemocyte-type proPO. Amino acid sequence analyses indicated that this enzyme was distinct from the known proPO. The cDNA sequence and deduced amino acid sequence of this enzyme has a putative binuclear copper center, and showed approximately 30% and 20% identity with the primary structures of reported proPO and haemocyanin sequences of the kuruma prawn, respectively. Reverse transcription PCR analysis showed that this enzyme was synthesized in the hepatopancreas rather than in haemocytes. Although the primary structure and enzymatic properties of this novel enzyme suggested that it is a phenoloxidase, its biogenesis, tissue distribution, and oligomeric state resemble those of haemocyanin, which belongs to the same protein family (type III copper protein). This novel proPO enzyme may share a role with the already characterized version, itself a major component of the innate immune system in crustaceans.