Biochemical characterization of a GH19 chitinase from Streptomyces alfalfae and its applications in crystalline chitin conversion and biocontrol.

Chitinases play crucial roles in enzymatic conversion of chitin and biocontrol of phytopathogenic fungi. Herein, a chitinase of glycoside hydrolase (GH) family 19, SaChiB, was cloned from Streptomyces alfalfae ACCC 40021 and expressed in Escherichia coli BL21(DE3). The purified SaChiB displayed maximal activities at 45 °C and pH 8.0, and showed good stability up to 55 °C and in the range of pH 4.0-11.0, respectively. It exhibited substrate specificity towards chitin and chitooligosaccharides (degree of polymerization 3-6) with the endo-cleavage manner. In combination with the N-acetyl hexosaminidase SaHEX, it yielded a conversion rate of 95.2% from chitin powder to N-acetyl-D-glucosamine in 8 h and a product purity of >98.5%. Furthermore, the enzyme strongly inhibited the growth of tested pathogenic fungi. These results indicated that SaChiB has the great potential for applications in the conversion of raw chitinous waste in industries as well as the biocontrol of fungal diseases in agriculture.

[Expression of miRNA let-7a and HMGA2 and Diagnostic Value of Serum miRNA let-7a Level in Pancreatic Cancer].

OBJECTIVE: To investigate the diagnostic value of miRNA let-7a, high mobility group A2 (HMGA2) expression and serum miRNA let-7a level in pancreatic cancer. METHODS: From January 2014 to January 2019, 60 patients with pancreatic cancer were collected for fresh pancreatic ductal adenocarcinoma tissue and normal pancreatic tissue adjacent to the cancer after the operation. Serum samples before and after operation were also collected, while 60 healthy people were enrolled as the control group. The expression of miRNA let-7a (qRT-PCR) and HMGA2 (qRT-PCR and Western blot) in cancer and adjacent normal tissues were measured. The serum level of miRNA let-7a was detected by qRT-PCR. The relationship between miRNA let-7a and HMGA2 expression and the clinicopathological features of pancreatic cancer was analyzed. The diagnostic value of serum miRNA let-7a pre-operation in patients with pancreatic cancer was also analyzed with ROC curve. RESULTS: Compared with normal tissues adjacent to the cancer, the expression level of miRNA let-7a in pancreatic cancer tissues decreased ( t=20.291, P<0.01), and the expression of HMGA2 mRNA increased ( t=46.681, P<0.01). The expression of HMGA2 protein in cancer tissues was higher than that in normal tissues adjacent to the cancer ( t=22.973, P<0.01). The serum level of miRNA let-7a in pancreatic cancer patients was significantly lower than that in healthy controls ( t=24.854, P<0.01). The relative level of serum miRNA let-7a at 1 week after surgery was significantly lower than that before surgery in pancreatic cancer patients ( t=6.885, P<0.01). There was a positive correlation between cancer tissue and serum miRNA let-7a expression 1 week after surgery ( r=0.411, P=0.000). The relative expression levels of miRNA let-7a and HMGA2 in pancreatic cancer tissues were significantly different in different TNM stages and lymph node metastasis ( P<0.05). The area under curve of pre-operation serum miRNA let-7a for the diagnosis of pancreatic cancer was 0.823 ( 95% confidence interval: 0.665-0.917); when the optimal cut-off value of miRNA let-7a was 0.614, the sensitivity was 82.3%, the specificity was 74.1%. CONCLUSION: The expression of HMGA2 may be involved in the invasion and metastasis of pancreatic cancer. The level of serum miRNA let-7a may provide a reference for the diagnosis and postoperative monitoring of pancreatic cancer.

[Cloning, expression and characterization of a new endo-ß-N-acetylglucosaminidase from Streptomyces alfalfae].

Endo-ß-N-acetylglucosaminidase is used widely in the glycobiology studies and industries. In this study, a new endo-ß-N-acetylglucosaminidase, designated as Endo SA, was cloned from Streptomyces alfalfae ACCC 40021 and expressed in Escherichia coli BL21 (DE3). The purified recombinant Endo SA exhibited the maximum activity at 35 ºC and pH 6.0, good thermo/pH stability and high specific activity (1.0×106 U/mg). It displayed deglycosylation activity towards different protein substrates. These good properties make EndoSA a potential tool enzyme and industrial biocatalyst.

Enhancing the atypical esterase promiscuity of the γ-lactamase Sspg from Sulfolobus solfataricus by substrate screening.

Promiscuous enzymes can be modified by protein engineering, which enables the catalysis of non-native substrates. γ-lactamase Sspg from Sulfolobus solfataricus is an enzyme with high activity, high stability, and pronounced tolerance of high concentrations of the γ-lactam substrate. These characteristics suggest Sspg as a robust enzymatic catalyst for the preparation of optically pure γ-lactam. This study investigated the modification of this enzyme to expand its application toward resolving chiral esters. γ-Lactamase-esterase conversion was performed by employing a three-step method: initial sequence alignment, followed by substrate screening, and protein engineering based on the obtained substrate-enzyme docking results. This process of fine-tuning of chemical groups on substrates has been termed "substrate screening." Steric hindrance and chemical reactivity of the substrate are major concerns during this step, since both are determining factors for the enzyme-substrate interaction. By employing this three-step method, γ-lactamase Sspg was successfully converted into an esterase with high enantioselectivity towards phenylglycidate substrates (E value > 300). However, since both wild-type Sspg and Sspg mutants did not hydrolyze para-nitrophenyl substrates (pNPs), this esterase activity was termed "atypical esterase activity." The γ-lactamase activity and stability of the Sspg mutants were not severely compromised. The proposed method can be applied to find novel multi-functional enzyme catalysts within existing enzyme pools.

Transcriptional Suppression of CPI-17 Gene Expression in Vascular Smooth Muscle Cells by Tumor Necrosis Factor, Krüppel-Like Factor 4, and Sp1 Is Associated with Lipopolysaccharide-Induced Vascular Hypocontractility, Hypotension, and Mortality.

Vasodilatory shock in sepsis is caused by the failure of the vasculature to respond to vasopressors, which results in hypotension, multiorgan failure, and ultimately patient death. Recently, it was reported that CPI-17, a key player in the regulation of smooth muscle contraction, was downregulated by lipopolysaccharide (LPS) in mesenteric arteries concordant with vascular hypocontractilty. While Sp1 has been shown to activate CPI-17 transcription, it is unknown whether Sp1 is involved in LPS-induced smooth muscle CPI-17 downregulation. Here we report that tumor necrosis factor (TNF) was critical for LPS-induced smooth muscle CPI-17 downregulation. Mechanistically, we identified two GC boxes as a key TNF response element in the CPI-17 promoter and demonstrated that KLF4 was upregulated by TNF, competed with Sp1 for the binding to the GC boxes in the CPI-17 promoter, and repressed CPI-17 transcription through histone deacetylases (HDACs). Moreover, genetic deletion of TNF or pharmacological inhibition of HDACs protected mice from LPS-induced smooth muscle CPI-17 downregulation, vascular hypocontractility, hypotension, and mortality. In summary, these data provide a novel mechanism of the transcriptional control of CPI-17 in vascular smooth muscle cells under inflammatory conditions and suggest a new potential therapeutic strategy for the treatment of vasodilatory shock in sepsis.

Biochemical characterization of a ß-N-acetylhexosaminidase from Streptomyces alfalfae and its application in the production of N-acetyl-d-glucosamine.

N-Acetyl-d-glucosamine (GlcNAc) is a valuable monosaccharide widely used in the medical, agricultural, biofuel, and food industries. Its efficient and environment-friendly production depends on the binary system of ß-N-acetylhexosaminidase (HEX) and chitinase. In the present study, a HEX of glycoside hydrolasefamily 20 was identified in Streptomyces alfalfae ACCC40021, and was overexpressed in Escherichia coli. The purified recombinant SaHEX showed maximal activities at 60°C and pH 5.5, and retained stable up to 45°C. The enzyme not only exhibited broad substrate specificity including p-nitrophenyl ß-N-acetylglucosaminide, p-nitrophenyl ß-N-acetylgalactosaminide, chitooligosaccharides and colloidal chitin, but also had higher specific activities (up to 1149.7 ± 72.6 U/mg) towards natural and synthetic substrates. When combined with a commercial chitinase, it achieved a conversion rate of 93.7% from 1% of colloidal chitin to GlcNAc in 6 h, with the product purity of >98%. These excellent properties make SaHEX a potential enzyme candidate for the chitin conversion for various industrial purposes.

Characterization of a recombinant (+)-γ-lactamase from Microbacterium hydrocarbonoxydans which provides evidence that two enantiocomplementary γ-lactamases are in the strain.

A two-step method, i.e., the transfer acyl analysis and then the chiral HPLC analysis, was employed in the screening of the cosmid library of Microbacterium hydrocarbonoxydans genome. Two enantiocomplementary γ-lactamase clones were found. A 40-kb cosmid showed (-)-γ-lactamase activity, and the activity was from Mhg which was reported previously according to the results of PCR identifying experiment. The 37-kb (+)-γ-lactamase cosmid was further constructed into a pUC18 plasmid library and screened by the same two-step method. A plasmid clone harboring a 1.6-kb fragment showed (+)-γ-lactamase activity. A 555-bp ORF in the 1.6-kb fragment showed high (+)-γ-lactamase activity when it was expressed under the control of T7 promoter. The coding protein showed significant homology with bacterial isochorismatase. The (+)-γ-lactamase was characterized and compared with the (-)-γ-lactamase Mhg. This is another report that two enantiocomplementary γ-lactamases are present in the same strain.

Purification and characterization of a novel NADPH-dependent 2-aminoacetophenone reductase from Arthrobacter sulfureus.

A novel 2-aminoacetophenone reductase was purified to homogeneity from Arthrobacter sulfureus BW1010. The enzyme is a monomer with a molecular weight of approximately 60 kDa. Using NADPH as coenzyme, it catalyzes the reduction of ketones, especially amine phenyl ketones, and stereospecifically reduces 2-aminoacetophenone to (S)-2-amino-1-phenylethanol (e.e > 99.8%) with the optimal pH at 7.5.

Smooth-muscle BMAL1 participates in blood pressure circadian rhythm regulation.

As the central pacemaker, the suprachiasmatic nucleus (SCN) has long been considered the primary regulator of blood pressure circadian rhythm; however, this dogma has been challenged by the discovery that each of the clock genes present in the SCN is also expressed and functions in peripheral tissues. The involvement and contribution of these peripheral clock genes in the circadian rhythm of blood pressure remains uncertain. Here, we demonstrate that selective deletion of the circadian clock transcriptional activator aryl hydrocarbon receptor nuclear translocator-like (Bmal1) from smooth muscle, but not from cardiomyocytes, compromised blood pressure circadian rhythm and decreased blood pressure without affecting SCN-controlled locomotor activity in murine models. In mesenteric arteries, BMAL1 bound to the promoter of and activated the transcription of Rho-kinase 2 (Rock2), and Bmal1 deletion abolished the time-of-day variations in response to agonist-induced vasoconstriction, myosin phosphorylation, and ROCK2 activation. Together, these data indicate that peripheral inputs contribute to the daily control of vasoconstriction and blood pressure and suggest that clock gene expression outside of the SCN should be further evaluated to elucidate pathogenic mechanisms of diseases involving blood pressure circadian rhythm disruption.

Autodisplay of an archaeal γ-lactamase on the cell surface of Escherichia coli using Xcc_Est as an anchoring scaffold and its application for preparation of the enantiopure antiviral drug intermediate (-) vince lactam.

At present, autotransporter protein mediated surface display has opened a new dimension in the development of whole-cell biocatalysts. Here, we report the identification of a novel autotransporter Xcc_Est from Xanthomonas campestris pv campestris 8004 by bioinformatic analysis and application of Xcc_Est as an anchoring motif for surface display of γ-lactamase (Gla) from thermophilic archaeon Sulfolobus solfataricus P2 in Escherichia coli. The localization of γ-lactamase in the cell envelope was monitored by Western blot, activity assay and flow cytometry analysis. Either the full-length or truncated Xcc_Est could efficiently transport γ-lactamase to the cell surface. Compared with the free enzyme, the displayed γ-lactamase exhibited optimum temperature of 30 °C other than 90 °C, with a substantial decrease of 60 °C. Under the preparation system, the engineered E. coli with autodisplayed γ-lactamase converted 100 g racemic vince lactam to produce 49.2 g (-) vince lactam at 30 °C within 4 h. By using chiral HPLC, the ee value of the produced (-) vince lactam was determined to be 99.5 %. The whole-cell biocatalyst exhibited excellent stability under the operational conditions. Our results indicate that the E. coli with surface displayed γ-lactamase is an efficient and economical whole cell biocatalyst for preparing the antiviral drug intermediate (-) vince lactam at mild temperature, eliminating expensive energy cost performed at high temperature.

[Survival analysis of patients with spontaneous rupture of hepatocellular carcinoma].

OBJECTIVE: To explore the prognostic factors influencing overall survival (OS) in patients with spontaneous rupture of hepatocellular carcinoma (HCC-SR). METHODS: The medical records of 44 patients with HCC-SR treated in our department from January 1, 2005 to April 1 2011 were retrospectively reviewed. The clinical and prognostic data of 19 HCC-SR patients who received curative hepatectomy were compared with data of 137 HCC patients with no SR who were managed by curative hepatectomy during the same period. Type of HCC-SR was defined according to previously established criteria. The clinicopathological data were evaluated for possible associations with OS of HCC-SR by univariate analysis with the Kaplan-Meier method followed by multivariate analysis with the Cox proportional hazard model. RESULTS: While some clinical features differed between the HCC-SR patients and non-HCC-SR patients, the postoperative prognosis was comparable between the two groups: (1) The 1-, 2-, 3- and 5-year postoperative cumulative recurrence rates were 78.9% (15/19), 89.5% (17/19), 94.7% (18/19) and 94.7% (18/19) in the HCC-SR group but 43.1% (59/137), 54.0% (74/137), 59.1% (81/137) and 66.4% (91/137) in the non-HCC-SR group respectively, and the differences reached statistical significance (P = 0.006, 0.003, 0.002, and 0.014); (2) The 1-, 2-, 3- and 5-year postoperative disease-free survival rates were 10.5% (2/19), 5.3% (1/19), 5.3% (1/19) and 5.3% (1/19) in the HCC-SR group but 40.1% (55/137), 21.2% (29/137), 12.4% (17/137) and 4.4% (6/137) in the non-HCC-SR group respectively, and only the 1-year disease-free survival rate was significantly different (P = 0.032); (3) The 1-, 2-, 3- and 5-year postoperative OS rates were 42.1% (8/19), 10.5% (2/19), 5.3% (1/19) and 5.3% (1/19) in the HCC-SR group but 59.1% (81/137), 32.8% (45/137), 19.0% (26/137) and 6.6% (9/137) in the non-HCC-SR group, and none of the differences reached statistical significance (P = 1.972, 0.061, 0.200, 1.000). Multivariate analysis identified that severity of concomitant liver cirrhosis, levels of alpha fetoprotein (AFP), choice of treatment modality, and type of HCC-SR acted as factors influencing OS. CONCLUSIONS: Patients with HCC-SR receiving curative hepatectomy have higher postoperative recurrence rates than their non-HCC-SR counterparts, but the two groups have similar postoperative OS rates. OS is influenced by severity of concomitant liver cirrhosis, level of AFP, choice of treatment modality, and type of HCC-SR.

[Fluorescence spectrum monitor for early warning of greenhouse cucumber aphis pests].

The infection and degree of cucumber aphis pests was studied by analyzing chlorophyllfluorescence spectrum in greenhouse. Based on the configuration of the spectrum, characteristic points were established, in which the intensity of waveband F632 was the first characteristic point between healthy and aphis pests leaves. The second characteristic point was K which was the change rate of spectral curve from waveband F512 to F632. The early warning could be executed on plants depending on these two points. The models of the infection and degrees of aphis pests were established for different wavebands by the least square support vector machine classification method (LSSVMR) radial basis function(RBF). The accuracy rate of classification and prediction of the models was compared by different peaks and valleys value in wavebands. The results indicated that the prediction accuracy of the model established by waveband F632 was the most perfect (96.34%).

[Chlorophyll fluorescence spectrum analysis of greenhouse cucumber disease and insect damage].

The present paper is based on chlorophyll fluorescence spectrum analysis. The wavelength 685 nm was determined as the primary characteristic point for the analysis of healthy or disease and insect damaged leaf by spectrum configuration. Dimensionality reduction of the spectrum was achieved by combining simple intercorrelation bands selection and principal component analysis (PCA). The principal component factor was reduced from 10 to 5 while the spectrum information was kept reaching 99.999%. By comparing and analysing three modeling methods, namely the partial least square regression (PLSR), BP neural network (BP) and least square support vector machine regression (LSSVMR), regarding correlation coefficient of true value and predicted value as evaluation criterion, eventually, LSSVMR was confirmed as the appropriate method for modeling of greenhouse cucumber disease and insect damage chlorophyll fluorescence spectrum analysis.

Smooth muscle-specific expression of calcium-independent phospholipase A2ß (iPLA2ß) participates in the initiation and early progression of vascular inflammation and neointima formation.

Whether group VIA phospholipase A(2) (iPLA(2)ß) is involved in vascular inflammation and neointima formation is largely unknown. Here, we report that iPLA(2)ß expression increases in the vascular tunica media upon carotid artery ligation and that neointima formation is suppressed by genetic deletion of iPLA(2)ß or by inhibiting its activity or expression via perivascular delivery of bromoenol lactone or of antisense oligonucleotides, respectively. To investigate whether smooth muscle-specific iPLA(2)ß is involved in neointima formation, we generated transgenic mice in which iPLA(2)ß is expressed specifically in smooth muscle cells and demonstrate that smooth muscle-specific expression of iPLA(2)ß exacerbates ligation-induced neointima formation and enhanced both production of proinflammatory cytokines and vascular infiltration by macrophages. With cultured vascular smooth muscle cell, angiotensin II, arachidonic acid, and TNF-α markedly induce increased expression of IL-6 and TNF-α mRNAs, all of which were suppressed by inhibiting iPLA(2)ß activity or expression with bromoenol lactone, antisense oligonucleotides, and genetic deletion, respectively. Similar suppression also results from genetic deletion of 12/15-lipoxygenase or inhibiting its activity with nordihydroguaiaretic acid or luteolin. Expression of iPLA(2)ß protein in cultured vascular smooth muscle cells was found to depend on the phenotypic state and to rise upon incubation with TNF-α. Our studies thus illustrate that smooth muscle cell-specific iPLA(2)ß participates in the initiation and early progression of vascular inflammation and neointima formation and suggest that iPLA(2)ß may represent a novel therapeutic target for preventing cardiovascular diseases.

Identification of a cAMP-response element in the regulator of G-protein signaling-2 (RGS2) promoter as a key cis-regulatory element for RGS2 transcriptional regulation by angiotensin II in cultured vascular smooth muscles.

Mice deficient in regulator of G-protein signaling-2 (RGS2) have severe hypertension, and RGS2 genetic variations occur in hypertensive humans. A potentially important negative feedback loop in blood pressure homeostasis is that angiotensin II (Ang II) increases vascular smooth muscle cell (VSMC) RGS2 expression. We reported that Group VIA phospholipase A(2) (iPLA(2)ß) is required for this response (Xie, Z., Gong, M. C., Su, W., Turk, J., and Guo, Z. (2007) J. Biol. Chem. 282, 25278-25289), but the specific molecular causes and consequences of iPLA(2)ß activation are not known. Here we demonstrate that both protein kinases C (PKC) and A (PKA) participate in Ang II-induced VSMC RGS2 mRNA up-regulation, and that actions of PKC and PKA precede and follow iPLA(2)ß activation, respectively. Moreover, we identified a conserved cAMP-response element (CRE) in the murine RGS2 promoter that is critical for cAMP-response element-binding protein (CREB) binding and RGS2 promoter activation. Forskolin-stimulated RGS2 mRNA up-regulation is inhibited by CREB sequestration or specific disruption of the CREB-RGS2 promoter interaction, and Ang II-induced CREB phosphorylation and nuclear localization are blocked by iPLA(2)ß pharmacologic inhibition or genetic ablation. Ang II-induced intracellular cyclic AMP accumulation precedes CREB phosphorylation and is diminished by inhibiting iPLA(2), cyclooxygenase, or lipoxygenase. Moreover, three single nucleotide polymorphisms identified in hypertensive patients are located in the human RGS2 promoter CREB binding site. Point mutations corresponding to these single nucleotide polymorphisms interfere with stimulation of human RGS2 promoter activity by forskolin. Our studies thus delineate a negative feedback loop to attenuate Ang II signaling in VSMC with potential importance in blood pressure homeostasis and the pathogenesis of human essential hypertension.

Thermostable D-carbamoylase from Sinorhizobium morelens S-5: purification, characterization and gene expression in Escherichia coli.

A d-carbamoylase from Sinorhizobium morelens S-5 was purified and characterized. The enzyme was purified 189-fold to homogeneity with a yield of 19.1% by aqueous two-phase extraction and two steps of column chromatography. The enzyme is a homotetramer with a native molecular mass of 150 kDa and a subunit relative molecular mass of 38 kDa. The optimum pH and temperature of the enzyme were pH 7.0 and 60 degrees C, respectively. The enzyme showed high thermal and oxidative stability. It was found to have a K(m) of 3.76 mM and a V(max) of 383 U/mg for N-carbamoyl-d-p-hydroxyphenylglycine. The hyuC gene coding for this enzyme was cloned, and its nucleotide sequence was determined. The deduced amino acid sequence encoded by the hyuC gene exhibited high homology to the amino acid sequences of d-carbamoylase from other sources. The gene could be highly expressed in Escherichia coli, and the product was purified to homogeneity from the recombinant. Our results show that the enzyme has great potential for industrial application.

Transformation of 2-aminoacetophenone to ( S) -2-amino-1-phenylethanol by Arthrobacter sulfureus.

A new isolate of Arthrobacter sulfureus , when incubated at 50 g resting cells (dry cell wt) l(-1) with 50 g glucose l(-1) and 1 g 2-aminoacetophenone l(-1) in 50 mm potassium buffer (pH 7, 4 ml) at 30 degrees C, produced ( S )-2-amino-1-phenylethanol (e.e. >99%) with 75% yield in 6 h.

A single residual replacement improves the folding and stability of recombinant cassava hydroxynitrile lyase in E. coil.

Substitution of Ser113 for Gly113 in the cap domain of hydroxynitrile lyase from Manihot esculenta (MeHNL) was performed by site-directed mutagenesis to improve its self-generated folding and stability under denaturation conditions. The yield of the recombinant mutant HNL1 (mut-HNL1), which had higher specific activity than the wild type HNL0 (wt-HNL0), was increased by 2 to 3-fold. Thermostability of MeHNL was also enhanced, probably due to an increase in content of the beta-strand secondary structure according to CD analysis. Our data in this report suggest that Ser113 significantly contributes to the in vivo folding and stability of MeHNL and demonstrates an economic advantage of mut-HNL1 over the wt-HNL0.