The doublecortin (DCX) gene encodes DCX, a microtubule-associated protein that plays a crucial role in brain development. DCX variants can disrupt microtubule binding and stabilization, interfere with intracellular transport, and affect post-translational modifications. A correlation exists between variant types and clinical severity. Animal models and induced pluripotent stem cell (iPSC) models simulating DCX deficiency revealed the dynamic progression of the disease, which has provided a powerful tool for investigating disease mechanisms and screening therapeutic agents. Currently there is no cure for DCX variants, with treatment primarily relying on anti-epileptic drugs and symptom management. Basic research is now offering new avenues for future therapeutic approaches. This article has summarized the potential pathogenic mechanisms and therapeutic strategies for the DCX variants, with an aim to provide insights for clinical treatment.
Humans ; Doublecortin Protein ; Doublecortin Domain Proteins ; Animals ; Neuropeptides/metabolism* ; Microtubule-Associated Proteins/metabolism* ; Mutation

The efficient production of L-glutamate is dependent on the product's rapid efflux, hence researchers have recently concentrated on artificially modifying its transport system and cell membrane wall structure. Considering the unique composition and structure of the cell wall of Corynebacterium glutamicum, we investigated the effects of CmpLs on L-glutamate synthesis and transport in SCgGC7, a constitutive L-glutamate efflux strain. First, the knockout strains of CmpLs were constructed, and it was confirmed that the deletion of CmpL1 and CmpL4 significantly improved the performance of L-glutamate producers. Next, temperature-sensitive L-glutamate fermentation with the CmpL1 and CmpL4 knockout strains were carried out in 5 L bioreactors, where the knockout strains showcased temperature-sensitive characteristics and enhanced capacities for L-glutamate production under high temperatures. Notably, the CmpL1 knockout strain outperformed the control strain in terms of L-glutamate production, showing production and yield increases of 69.2% and 55.3%, respectively. Finally, the intracellular and extracellular metabolites collected at the end of the fermentation process were analyzed. The modification of CmpLs greatly improved the L-glutamate excretion and metabolic flux for both L-glutamate production and transport. Additionally, the CmpL1 knockout strain showed decreased accumulation of downstream metabolites of L-glutamate and intermediate metabolites of tricarboxylic acid (TCA) cycle, which were consistent with its high L-glutamate biosynthesis capacity. In addition to offering an ideal target for improving the stability and performance of the industrial strains for L-glutamate production, the functional complementarity and redundancy of CmpLs provide a novel target and method for improving the transport of other metabolites by modification of the cell membrane and cell wall structures in C. glutamicum.
Corynebacterium glutamicum/genetics* ; Glutamic Acid/biosynthesis* ; Fermentation ; Metabolic Engineering ; Bacterial Proteins/metabolism* ; Bioreactors/microbiology* ; Gene Knockout Techniques

Glucose oxidase (GOD) is an oxygen-consuming dehydrogenase that can catalyze the production of gluconic acid hydrogen peroxide from glucose, and its specific mechanism of action makes it promising for applications, while the low catalytic activity and poor thermostability have become the main factors limiting the industrial application of this enzyme. In this study, we used the glucose oxidase AtGOD reported with the best thermostability as the source sequence for phylogenetic analysis to obtain the GOD with excellent performance. Six genes were screened and successfully synthesized for functional validation. Among them, the glucose oxidase AhGODB derived from Aspergillus heteromorphus was expressed in Pichia pastoris and showed better thermostability and catalytic activity, with an optimal temperature of 40 ℃, a specific activity of 112.2 U/mg, and a relative activity of 47% after 5 min of treatment at 70 ℃. To improve its activity and thermal stability, we constructed several mutants by directed evolution combined with rational design. Compared with the original enzyme, the mutant T72R/A153P showcased the optimum temperature increasing from 40 to 50 ℃, the specific activity increasing from 112.2 U/mg to 166.1 U/mg, and the relative activity after treatment at 70 ℃ for 30 min increasing from 0% to 33%. In conclusion, the glucose oxidase mutants obtained in this study have improved catalytic activity and thermostability, and have potential for application.
Glucose Oxidase/chemistry* ; Enzyme Stability ; Aspergillus/genetics* ; Pichia/metabolism* ; Temperature ; Catalysis ; Fungal Proteins/metabolism* ; Hot Temperature

Screening carbonyl reductases with the ability to catalyze the reduction of complex carbonyl compounds is of great significance for the biosynthesis of R-tolvaptan(R-TVP). In this study, the target carbonyl reductase in the crude enzyme extract of rabbit liver was separated, purified, and identified by ammonium sulfate precipitation, gel-filtration chromatography, ion exchange chromatography, affinity chromatography, and protein mass spectrometry. With the rabbit liver genome as the template, the gene encoding the carbonyl reductase rlsr5 was amplified by PCR and the recombinant strain was successfully constructed. After RLSR5 was purified by affinity chromatography, its enzymatic properties were characterized. The results indicated that the gene sequence of rlsr5 was 972 bp, encoding a protein with a molecular weight of 40 kDa. RLSR5 was a dimeric protein, and each monomer was composed of a (α/β)₈-barrel structure. RLSR5 could asymmetrically reduce 7-chloro-1-[2-methyl-4-[(2- methylbenzoyl)amino]benzoyl]-5-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine (prochiral ketone, PK) to synthesize R-TVP. The specific activity of the enzyme was 36.64 U/mg, and the optical purity of the product was 99%. This enzyme showcased the optimal performance at pH 6.0 and 30 °C. It was independent of metal ions, with the activity enhanced by Mn²⁺. This study lays a foundation for the biosynthesis of tolvaptan of optical grade.
Animals ; Rabbits ; Alcohol Oxidoreductases/biosynthesis* ; Recombinant Proteins/metabolism* ; Escherichia coli/metabolism* ; Liver/enzymology*

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*

Transcriptional regulation based on transcription factors is an effective regulatory method widely used in microbial cell factories. Currently, few naturally transcriptional regulatory elements have been discovered from Saccharomyces cerevisiae and applied. Moreover, the discovered elements cannot meet the demand for specific metabolic regulation of exogenous compounds due to the high background expression or narrow dynamic ranges. There are abundant transcriptional regulatory elements in plants. However, the sequences and functions of most elements have not been fully characterized and optimized. Particularly, the applications of these elements in microbial cell factories are still in the infancy stage. In this study, natural regulatory elements from Medicago truncatula were selected, including the transcription factors MtTASR2 and MtTASR3, along with their associated promoter P_roHMGR1, for functional characterization and engineering modification. We constructed an inducible transcriptional regulation tool and applied it in the regulation of heterologous β-carotene synthesis in S. cerevisiae, which increased the β-carotene production by 7.31 folds compared with the original strain. This study demonstrates that plant-derived transcriptional regulatory elements can be used to regulate the expression of multiple genes in S. cerevisiae, providing new strategies and ideas for the specific regulation and application of these elements in microbial cell factories.
Medicago truncatula/metabolism* ; Saccharomyces cerevisiae/metabolism* ; Transcription Factors/genetics* ; beta Carotene/biosynthesis* ; Promoter Regions, Genetic/genetics* ; Gene Expression Regulation, Plant ; Metabolic Engineering/methods* ; Regulatory Elements, Transcriptional/genetics* ; Plant Proteins/genetics*

Wickerhamomyces ciferrii (W.c), an unconventional heterothallic yeast species, is renowned for its high production of tetraacetyl phytosphingosine (TAPS). Due to its excellent performance in TAPS production, this study aimed to construct a genetic operating system of W.c to enhance the production of TAPS and to screen high-yielding strains by mutagenesis and genetic engineering, thus laying the foundation for further development of industrial production of sphingolipid metabolites. In this study, we selected two autonomous replication elements (CEN, 2μ) and mined 11 endogenous promoter elements to establish a genetic operating system in W. ciferrii. The overexpression of Syr2 and Lcb2 in the sphingolipid metabolism pathway significantly increased the production of TAPS. Meanwhile, we established a method for the identification of haploid mating types of W. ciferrii by combining RT-PCR and flow cytometry. Five strains of W. ciferrii with different mating types constructed from the standard diploid W. ciferrii ATCC 14091 were screened out. A-type haploid W.c 140 showcased the highest production of TAPS with a yield of 4.74 mg/g and a titer of 32.61 mg/L. Mutant strains W.c 140-A9 and W.c 140-A11 were induced by atmospheric pressure room temperature plasma mutagenesis. The recombinant strains W.c 140 OELcb2 and W.c 140 OESyr2 with overexpression were constructed with the genetic operating system established in this study. The TAPS yields of the mutant strains increased by 61.39% and 67.09%, respectively, compared with that of starting strain W.c 140. The recombinant strains cultured in the LCBNB medium achieved yields of 10.60 mg/g and 12.14 mg/g, respectively, representing 2.24 and 2.56 times of that in strain W.c 140. Moreover, the yields of the two recombinant strains were significantly higher than that of the diploid strain ATCC 14091. The genetic operating system and the haploid strain W.c 140 established in this study provide a basis for the subsequent establishment of genetic engineering tools for W. ciferrii.
Sphingosine/genetics* ; Saccharomycetales/metabolism* ; Genetic Engineering/methods* ; Promoter Regions, Genetic ; Metabolic Engineering/methods* ; Fungal Proteins/genetics*

Biosensors have become powerful tools for real-time monitoring of specific small molecules and precise control of gene expression in biological systems. High-throughput sensors for 1, 4-butanediamine biosynthesis can greatly improve the screening efficiency of high-yielding 1, 4-butanediamine strains. However, the strategies for adapting the characteristics of biosensors are still rarely studied, which limits the applicability of 1, 4-butanediamine biosensors. In this paper, we propose the development of a 1, 4-butanediamine biosensor based on the transcriptional regulator PuuR, whose homologous operator puuO is installed in the constitutive promoter P_gapA of Escherichia coli to control the expression of the downstream superfolder green fluorescent protein (sfGFP) as the reporter protein. Finally, the biosensor showed a stable linear relationship between the GFP/OD₆₀₀ value and the concentration of 1, 4-butanediamine when the concentration of 1, 4-butanediamine was 0-50 mmol/L. The promoters with different strengths in the E. coli genome were used to modify the 1, 4-butanediamine biosensor, and the functional properties of the PuuR-based 1, 4-butanediamine biosensor were explored and improved, which laid the groundwork for high-throughput screening of engineered strains highly producing 1, 4-butanediamine.
Biosensing Techniques/methods* ; Escherichia coli/metabolism* ; Promoter Regions, Genetic/genetics* ; Green Fluorescent Proteins/metabolism* ; Transcription Factors/genetics* ; Escherichia coli Proteins/genetics* ; Diamines/metabolism* ; Gene Expression Regulation, Bacterial

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