The high content of sucrose and raffinose reduces the prebiotic value of soybean oligosaccharides. Fructan sucrases can catalyze the conversion of sucrose and raffinose to high-value products such as fructooligosaccharides and melibiose. To obtain a fructan sucrase that can efficiently convert soybean oligosaccharides, we first mined the fructan sucrase gene from microorganisms in the coastal areas of Xisha Islands and Bohai Bay and then characterized the enzymatic and catalytic properties of the enzyme. Finally, recombinant extracellular expression of this gene was carried out in Bacillus subtilis. The results showed that a novel fructan sucrase, BhLS 39, was mined from Bacillus halotolerans. With sucrose and raffinose as substrates, BhLS 39 showed the optimal temperatures of 50 ℃ and 55 ℃, optimal pH 5.5 for both, and K_cat/K_m ratio of 3.4 and 6.6 L/(mmol·s), respectively. When 400 g/L raffinose was used as the substrate, the melibiose conversion rate was 84.6% after 30 min treatment with 5 U BhLS 39. Furthermore, BhLS 39 catalyzed the conversion of sucrose to produce levan-type-fructooligosaccharide and levan. Then, the recombinant extracellular expression of BhLS 39 in B. subtilis was achieved. The co-expression of the intracellular chaperone DnaK and the extracellular chaperone PrsA increased the extracellular activity of the recombinant BhLS 39 by 5.2 folds to 17 U/mL compared with that of the control strain. BhLS 39 obtained in this study is conducive to improving the quality and economic benefits of soybean oligosaccharides. At the same time, the strategy used here to enhance the extracellular expression of BhLS 39 will also promote the efficient recombinant expression of other proteins in B. subtilis.
Oligosaccharides/metabolism* ; Glycine max/metabolism* ; Bacillus subtilis/metabolism* ; Sucrase/biosynthesis* ; Raffinose/metabolism* ; Fructans/metabolism* ; Sucrose/metabolism* ; Bacillus/genetics* ; Recombinant Proteins/biosynthesis* ; Bacterial Proteins/biosynthesis*

To screen and identify a chitosanase with high stability, we cloned the chitosanase gene from Bacillus atrophaeus with a high protease yield from the barren saline-alkali soil and expressed this gene in Escherichia coli. The expressed chitosanase of B. atrophaeus (BA-CSN) was purified by nickel-affinity column chromatography. The properties including optimal temperature, optimal pH, substrate specificity, and kinetic parameters of BA-CSN were characterized. The results showed that BA-CSN had the molecular weight of 31.13 kDa, the optimal temperature of 55 ℃, the optimal pH 5.5, and good stability at temperatures below 45 ℃ and pH 4.0-9.0. BA-CSN also had good stability within 4 h of pH 3.0 and 10.0, be activated by K⁺, Na⁺, Mn²⁺, Ca²⁺, Mg²⁺, and Co²⁺, (especially by Mn²⁺), and be inhibited by Fe³⁺, Cu²⁺, and Ag⁺. BA-CSN showcased the highest relative activity in the hydrolysis of colloidal chitosan, and it had good hydrolysis ability for colloidal chitin. Under the optimal catalytic conditions, BA-CSN demonstrated the Michaelis constant K_m and maximum reaction rate V_max of 9.94 mg/mL and 26.624 μmoL/(mL·min), respectively, for colloidal chitosan. In short, BA-CSN has strong tolerance to acids and alkali, possessing broad industrial application prospects.
Bacillus/genetics* ; Hydrogen-Ion Concentration ; Escherichia coli/metabolism* ; Glycoside Hydrolases/biosynthesis* ; Substrate Specificity ; Enzyme Stability ; Chitosan/metabolism* ; Temperature ; Kinetics ; Cloning, Molecular ; Bacterial Proteins/biosynthesis* ; Recombinant Proteins/genetics*

S-methyl-L-cysteine sulfoxide (SMCO) is a non-protein sulfur-containing amino acid with a variety of functions. There are few reports on the enzymes catalyzing the biosynthesis of SMCO from S-methyl-L-cysteine (SMC). In this study, the flavin-containing monooxygenase gene derived from Schizosaccharomyces pombe (spfmo) was heterologously expressed in Escherichia coli BL21(DE3) and the enzymatic properties of the expressed protein were analyzed. The optimum catalytic conditions of the recombinant SpFMO were 30 ℃ and pH 8.0, under which the enzyme activity reached 72.77 U/g. An appropriate amount of Mg²⁺ improved the enzyme activity. The enzyme kinetic analysis showed that the K_m and k_cat/K_m of SpFMO on the substrate SMC were 23.89 μmol/L and 61.71 L/(min·mmol), respectively. Under the optimal reaction conditions, the yield of SMCO synthesized from SMC catalyzed by SpFMO was 12.31% within 9 h. This study provides reference for the enzymatic synthesis of SMCO.
Schizosaccharomyces/genetics* ; Escherichia coli/metabolism* ; Recombinant Proteins/metabolism* ; Cysteine/biosynthesis* ; Mixed Function Oxygenases/metabolism* ; Schizosaccharomyces pombe Proteins/metabolism* ; Oxygenases/metabolism* ; Kinetics

Endotoxins are common exogenous pyrogens. Excessive endotoxins in medical devices and injections can lead to serious consequences such as sepsis, septic shock, and even death. Therefore, endotoxin detection plays a crucial role in medical, pharmaceutical, and food sectors. The wide application of Limulus amebocyte lysate (LAL) has led to a sharp decline in the number of horseshoe crabs. Moreover, the LAL assay has limitations such as interbatch variations and difficulty in quantification. The recombinant factor C (rFC) assay is stable between batches, highly sensitive, and capable of quantitation, and thus it can be used as an alternative for the LAL assay. However, the high cost and complex procedures involved in producing recombinant factor C have limited the widespread application of this method. In order to simplify the preparation and reduce the production cost of recombinant factor C, this study focuses on the production of recombinant factor C based on the baculovirus expression system. Multiple measures such as a high-yield and anti-apoptotic vector qBac-IIIG, the optimal signal peptide, and the optimized codon were used to reach the goal of endotoxin detection with cell supernatant. This method simplifies the steps of protein purification. The sensitivity of the supernatant reached 0.05 EU/mL in a 1-L fermentation system, and 500 000 detecting reactions can be supported per liter of fermentation broth. This study increases the yield and activity of recombinant factor C, simplifies the procedures of protein purification, and reduces the cost, laying a foundation for the promotion and application of recombinant factor C in endotoxin detection.
Animals ; Recombinant Proteins/genetics* ; Horseshoe Crabs/chemistry* ; Baculoviridae/metabolism* ; Endotoxins/analysis* ; Protein C/biosynthesis* ; Genetic Vectors/genetics* ; Arthropod Proteins/genetics* ; Enzyme Precursors ; Serine Endopeptidases

To prepare antibodies that specifically recognize the conserved domain in the large extracellular loop of the CD63 protein, we expressed anti-CD63 single-chain variable fragment (scFv) antibody in Pichia pastoris in a secreted form. The purified expression product was found to bind specifically with CD63 protein and recognize CD63 on the surface of SK-MEL-28 cells. The variable region of the anti-CD63 monoclonal antibody in an anti-CD63-positive cell line was sequenced. The anti-CD63 scFv consisted of a variable heavy chain and a variable light chain linked by a flexible peptide was then designed. After codon optimization, the gene was synthesized and cloned into the expression plasmid pPICZα-A. The SacI-linearized plasmid was electroporated into P. pastoris X33, and 1% methanol were used to induce the expression of scFv. The fermentation supernatant was purified by Ni column. Anti-CD63 scFv was identified by SDS-PAGE and Western blotting, and its biological activities were analyzed by immunoblotting, immunofluorescence, cell-based ELISA, and flow cytometry. A P. pastoris strain capable of expressing and secreting anti-CD63 scFv was successfully obtained. The antibody had a molecular weight of approximately 30 kDa and specifically recognized CD63 protein. The expression of anti-CD63 scFv in P. pastoris paves the way for the production of anti-CD63 antibodies on a large-scale, which is undoubtedly an economical and effective way of antibody acquisition.
Single-Chain Antibodies/immunology* ; Humans ; Tetraspanin 30/immunology* ; Recombinant Proteins/immunology* ; Pichia/genetics* ; Saccharomycetales/metabolism*

Collagen, a vital matrix protein for various tissue and functions in animals, is widely applied in biomaterials. In type Ⅰ collagen, missense mutations of glycine (Gly) in the Gly-Xaa-Yaa triplet of the triple helix are a major cause of osteogenesis imperfecta (OI). Clinical manifestations exhibit marked heterogeneity, spanning a broad disease spectrum from mild skeletal fragility (Type Ⅰ) to severe limb deformities (Type Ⅲ) and perinatal lethal forms (Type Ⅱ). This study utilized recombinant collagen as a model to further elucidate whether Gly→Ala/Val mutations at the N-terminus of the integrin-binding sequence GFPGER affect collagen structure and function, and to explore the underlying mechanisms by which missense mutations impact the biological function of collagen. By introducing Ala and Val substitutions at seven Gly positions N-terminal to the GFPGER sequence, we systematically assessed the effects of these amino acid replacements on the triple-helical structure, thermal stability, integrin-binding ability, and cell adhesion of recombinant collagen. All constructs formed a stable triple-helix structure, with slightly compromised thermal stability. Gly→Val substitutions increased the susceptibility of recombinant collagen to trypsin, which suggested local conformational perturbations in the triple helix. In addition, Gly→Val substitutions significantly reduced the integrin-binding affinity and decreased HT1080 cell adhesion, with the effects stronger than Gly→Ala substitutions. Compared with Gly→Ala substitutions, substitution of Gly with the larger residue Val had enhanced negative effects on the structure and function of recombinant collagen. These findings provide new insights into the molecular mechanisms of osteogenesis imperfecta and offer theoretical references and experimental foundations for the design of collagen sequences and the development of collagen-based biomaterials.
Recombinant Proteins/biosynthesis* ; Glycine/genetics* ; Humans ; Osteogenesis Imperfecta/genetics* ; Integrins/metabolism* ; Collagen/metabolism* ; Collagen Type I/metabolism* ; Amino Acid Substitution ; Mutation ; Mutation, Missense

Carbamate pesticides, a new type of broad-spectrum pesticides for controlling pests, mites, and weeds, are developed to address the shortcomings of organochlorine and organophosphorus pesticides. Their widespread use and slow degradation have led to environmental pollution, causing damage to ecosystems and human health. Managing pesticide residues is a pressing issue in the current environmental protection. This study aims to investigate the expression of SyEst870, a member of the SGNH/GDSL hydrolase family in Sphingobium yanoikuyae, in a prokaryotic system and evaluate the ability of the recombinant protein to degrade carbamate pesticides. The prokaryotic expression vector pET-32a-SyEst870 was constructed and transformed into the Escherichia coli BL21 for heterologous expression. The purified protein was studied in terms of enzyme activity and effects of temperature, pH, and metal ions on the enzyme activity, with p-nitrophenol acetate as the substrate and based on the standard curve of p-nitrophenol. LC-MS (liquid chromatography-mass spectrometry) was employed to examine the degradation effects of SyEst870 on carbaryl, metolcarb, and isoprocarb. GC-MS (gas chromatography-mass spectrometry) was employed to detect the degradation products of SyEst870 for the three pesticides. The soluble protein SyEst870 was successfully obtained through the heterologous expression in Escherichia coli, which yielded an enzyme with the activity of 677.5 U after affinity chromatography. SyEst870 exhibited degradation rates of 82.34%, 84.43%, and 92.87% for carbaryl, metolcarb, and isoprocarb, respectively, at an initial concentration of 100 mg/L within 24 h at 30 ℃ and pH 7.0. The primary degradation products of carbaryl were identified as α-naphthol and methyl isocyanate. Metolcarb was mainly degraded into m-cresol and methyl isocyanate, and isoprocarb was mainly degraded into 2-isopropylphenol and methyl isocyanate. Compared with the half-life of carbamate pesticides in the natural environment, which ranges from a few days to several weeks, the recombinant protein SyEst870 can rapidly eliminate the residues of carbamate pesticides. This study lays a foundation for addressing pesticide residues in the environment and in fruits and vegetables.
Escherichia coli/metabolism* ; Sphingomonadaceae/genetics* ; Recombinant Proteins/metabolism* ; Biodegradation, Environmental ; Esterases/metabolism* ; Pesticides/isolation & purification* ; Carbamates/isolation & purification*

Human keratinocyte growth factor-1 (hKGF-1), a member of the fibroblast growth factor (FGF) family, plays crucial roles in organ development, cell proliferation, wound healing, and tissue repair, representing one of the most effective and specific growth factors for skin repair. However, obtaining recombinant hKGF-1 remains challenging due to its universally low expression efficiency in vitro. This study employs the Bombyx mori baculovirus expression system to establish a technological platform that utilizes the economically important insect Bombyx mori as a bioreactor for high-efficiency and low-cost expression and production of recombinant human keratinocyte growth factor 1 (hKGF-1) protein, ultimately achieving high-level expression of hKGF-1 in Bombyx mori ovary cell line (BmN). In this study, we optimized the hKGF-1 sequence based on the codon preference of baculovirus. By fusing hKGF-1 with polyhedrin (highly expressed in this system) and adding extra promoters and enhancers, we significantly improved the expreesion level of hKGF-1 in Bombyx mori cells. The results demonstrated that the aforementioned strategies significantly enhanced the expression level of hKGF-1 in Bombyx mori cells. SDS-PAGE and Western blotting results revealed that the highest hKGF-1 expression (accounting for 8.7% of total cellular protein) was achieved when the Polh promoter was combined in tandem with the P6.9 promoter and hKGF-1 was fused with a 15-residue polyhedrin fragment for co-expression. The optimal harvest time was determined to be 120 h post transfection. This study achieved the efficient expression of hKGF-1 in Bombyx mori cells, establishing an ideal technological platform for the industrial utilization of recombinant hKGF-1. The developed methodology not only provides valuable technical references for the production of other growth factors and complex proteins, but also demonstrates significant implications for employing silkworms as bioreactors for recombinant human protein expression.
Bombyx/metabolism* ; Animals ; Baculoviridae/metabolism* ; Humans ; Fibroblast Growth Factor 7/biosynthesis* ; Recombinant Proteins/genetics* ; Cell Line ; Genetic Vectors/genetics*

The Chinese hamster ovary (CHO) cell is the most representative mammalian cell protein expression system, and it is widely used in recombinant protein, vaccine and other biopharmaceutical fields. However, due to its vulnerability to environmental factors, apoptosis, and metabolic inhibitors, CHO cells demonstrate poor robustness, and thus the integrated viable cell density and unit cell productivity are largely limited. To improve the robustness and foreign protein expression efficiency of CHO cells, we employed CRISPR/Cas9 to knock out the apoptosis genes Bax and Bak and the lactate dehydrogenase gene LDHa, thereby blocking apoptosis and lactic acid metabolism pathways. The results of apoptosis and single cell viability detection showed that the number of apoptotic cells in the knockout cell lines Bax^-/-, Bax-bak^-/-, and LDHa-Bax-bak^-/- was reduced by 22.51%, 37.73%, and 64.12%, respectively, compared with the wild-type cell line CHO-K1, which indicated that the anti-apoptotic ability was significantly improved. After staurosporine treatment, the single cell viability of Bax^-/-, Bax-bak^-/-, and LDHa-Bax-bak^-/- cells was increased by 30.8%, 22%, and 41.1%, respectively. After treatment with puromycin, the single cell viability of Bax^-/-, Bax-bak^-/-, and LDHa-Bax-bak^-/- cells was increased by 26.7%, 30.7%, and 38.8%, respectively. To further investigate the production performance of cells obtained after blocking apoptosis and lactic acid metabolism pathways, we induced transient expression of human tissue plasminogen activator (tPA) in these cells. The results showed that the secretion of tPA in Bax^-/-, Bax-Bak^-/-, and LDHa-Bax-Bak^-/- cells was 11.12%, 46.18%, and 63.13%, respectively, higher than that in wild-type CHO-K1 cells. The expression of intracellular tPA was increased by 35.65%, 130%, and 192.15%. In conclusion, blocking apoptosis and lactic acid metabolism pathways simultaneously can improve cell robustness and productivity, with the performance better than blocking the apoptosis pathway alone. The above results indicated that the constructed cell lines were expected to be the delivery carriers of protein drugs such as medicinal peptides, and better used for the treatment of diseases.
CHO Cells ; Cricetulus ; Animals ; Apoptosis/genetics* ; Lactic Acid/metabolism* ; Recombinant Proteins/biosynthesis* ; L-Lactate Dehydrogenase/genetics* ; bcl-2-Associated X Protein/genetics* ; bcl-2 Homologous Antagonist-Killer Protein/genetics* ; Cricetinae ; CRISPR-Cas Systems ; Staurosporine/pharmacology*

Phenylpyruvic acid (PPA) is used as a food and feed additive and has a wide range of applications in the pharmaceutical, chemical and other fields. At present, PPA is mainly produced by chemical synthesis. With the green transformation of the manufacturing industry, biotransformation will be a good alternative for PPA production. The L-amino acid deaminase (PmiLAAD) from Proteus mirabilis has been widely studied for the production of PPA. However, the low yield limits its industrial production. To further enhance the production of PPA and better meet industrial demands, a more efficient synthesis method for PPA was established. In this study, PmiLAAD was heterologously expressed in Escherichia coli. Subsequently, a colorimetric reaction method was established to screen the strains with high PPA production. The semi-rational design of PmiLAAD was carried out, and the obtained triple-site mutant V18 (V437I/S93C/E417A) showed a 35% increase in catalytic activity compared with the wild type. Meanwhile, the effect of N-terminal truncation on the catalytic activity of the V18 mutant was investigated. After the optimization of the whole-cell conditions for the obtained mutant V18-N7, fed-batch conversion was carried out in a 5-L fermenter, and 44.13 g/L of PPA was synthesized with a conversion rate of 88%, which showed certain potential for industrial application. This study lays foundation for the industrial production of phenylpyruvic acid and also offers insights into the biosynthesis of other chemicals.
Escherichia coli/metabolism* ; Proteus mirabilis/genetics* ; Phenylpyruvic Acids/metabolism* ; Protein Engineering/methods* ; Recombinant Proteins/biosynthesis* ; Bacterial Proteins/metabolism*