Development of a rapid high-efficiency scalable process for acetylated Sus scrofa cationic trypsin production from Escherichia coli inclusion bodies

A methodological exploration of distinguishing hair quality based on hair proteomics

Hair is an advantageous biological sample due to its recordable, collectable, and storable nature. Hair's primary components are keratin and keratin-associated proteins. Owing to its abundance of cystine, keratin possesses impressive mechanical strength and chemical stability, formed by creating disulfide bonds as crosslinks within the protein peptide chain. Furthermore, keratin is cross-linked with keratin-associated proteins to create a complex network structure that provides the hair with strength and rigidity. Protein extraction serves as the foundation for hair analysis research. Bleaching hair causes damage to the structure between keratin and keratin-associated proteins, resulting in texture issues and hair breakage. This article outlines various physical treatment methods and lysate analysis that enhance the efficiency of hair protein extraction. The PLEE method achieves a three-fold increase in hair protein extraction efficiency when using a lysis solution containing SDS and combining high temperatures with intense shaking, compared to previous methods found in literature. We utilized the PLEE method to extract hair from both normal and damaged groups. Normal samples identified 156-157 proteins, including 51 keratin and keratin-associated proteins. The damaged group consisted of 155-158 identified proteins, of which 48-50 were keratin and keratin-associated proteins. Bleaching did not cause any notable difference in the protein identification of hair. However, it did reduce coverage of keratin and keratin-associated proteins significantly. Our hair protein extraction method provides extensive coverage of the hair proteome. Our findings indicate that bleaching damage results in subpar hair quality due to reduced coverage of protein primary sequences in keratin and keratin-associated proteins.

Mirror-image trypsin digestion and sequencing of D-proteins

The development of mirror-image biology systems and related applications is hindered by the lack of effective methods to sequence mirror-image (D-) proteins. Although natural-chirality (L-) proteins can be sequenced by bottom-up liquid chromatography-tandem mass spectrometry (LC-MS/MS), the sequencing of long D-peptides and D-proteins with the same strategy requires digestion by a site-specific D-protease before mass analysis. Here we apply solid-phase peptide synthesis and native chemical ligation to chemically synthesize a mirror-image version of trypsin, a widely used protease for site-specific protein digestion. Using mirror-image trypsin digestion and LC-MS/MS, we sequence a mirror-image large subunit ribosomal protein (L25) and a mirror-image Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4), and distinguish between different mutants of D-Dpo4. We also perform writing and reading of digital information in a long D-peptide of 50 amino acids. Thus, mirror-image trypsin digestion in conjunction with LC-MS/MS may facilitate practical applications of D-peptides and D-proteins as potential therapeutic and informational tools.

Phosphoproteome reveals long-term potentiation deficit following treatment of ultra-low dose soman exposure in mice

Soman, a warfare nerve agent, poses a significant threat by inducing severe brain damage that often results in death. Nonetheless, our understanding of the biological changes underlying persistent neurocognitive dysfunction caused by low dosage of soman remains limited. This study used mice to examine the effects of different doses of soman over time. Phosphoproteomic analysis of the mouse brain is the first time to be used to detect toxic effects of soman at such low or ultra-low doses, which were undetectable based on measuring the activity of acetylcholinesterase at the whole-animal level. We also found that phosphoproteome alterations could accurately track the soman dose, irrespective of the sampling time. Moreover, phosphoproteome revealed a rapid and adaptive cellular response to soman exposure, with the points of departure 8-38 times lower than that of acetylcholinesterase activity. Impaired long-term potentiation was identified in phosphoproteomic studies, which was further validated by targeted quantitative proteomics, immunohistochemistry, and immunofluorescence analyses, with significantly increased levels of phosphorylation of protein phosphatase 1 in the hippocampus following soman exposure. This increase in phosphorylation inhibits long-term potentiation, ultimately leading to long-term memory dysfunction in mice.

Using transcriptomics, proteomics and phosphoproteomics as new approach methodology (NAM) to define biological responses for chemical safety assessment

Omic-based technologies are of particular interest and importance for hazard identification and health risk characterization of chemicals. Their application in the new approach methodologies (NAMs) anchored on cellular toxicity pathways is based on the premise that any apical health endpoint change must be underpinned by some alterations at the omic levels. In the present study we examined the cellular responses to two chemicals, caffeine and coumarin, by generating and integrating multi-omic data from multi-dose and multi-time point transcriptomic, proteomic and phosphoproteomic experiments. We showed that the methodology presented here was able to capture the complete chain of events from the first chemical-induced changes at the phosphoproteome level, to changes in gene expression, and lastly to changes in protein abundance, each with vastly different points of departure (PODs). In HepG2 cells we found that the metabolism of lipids and general cellular stress response to be the dominant biological processes in response to caffeine and coumarin exposure, respectively. The phosphoproteomic changes were detected early in time, at very low doses and provided a fast, adaptive cellular response to chemical exposure with 7-37-fold lower points of departure comparing to the transcriptomics. Changes in protein abundance were found much less frequently than transcriptomic changes. While challenges remain, our study provides strong and novel evidence supporting the notion that these three omic technologies can be used in an integrated manner to facilitate a more complete understanding of pathway perturbations and POD determinations for risk assessment of chemical exposures.

A unique self-truncation of bacterial GH5 endoglucanases leads to enhanced activity and thermostability

Background

β-1,4-endoglucanase (EG) is one of the three types of cellulases used in cellulose saccharification during lignocellulosic biofuel/biomaterial production. GsCelA is an EG secreted by the thermophilic bacterium Geobacillus sp. 70PC53 isolated from rice straw compost in southern Taiwan. This enzyme belongs to glycoside hydrolase family 5 (GH5) with a TIM-barrel structure common among all members of this family. GsCelA exhibits excellent lignocellulolytic activity and thermostability. In the course of investigating the regulation of this enzyme, it was fortuitously discovered that GsCelA undergoes a novel self-truncation/activation process that appears to be common among GH5 enzymes.

Results

Three diverse Gram-positive bacterial GH5 EGs, but not a GH12 EG, undergo an unexpected self-truncation process by removing a part of their C-terminal region. This unique process has been studied in detail with GsCelA. The purified recombinant GsCelA was capable of removing a 53-amino-acid peptide from the C-terminus. Natural or engineered GsCelA truncated variants, with up to 60-amino-acid deletion from the C-terminus, exhibited higher specific activity and thermostability than the full-length enzyme. Interestingly, the C-terminal part that is removed in this self-truncation process is capable of binding to cellulosic substrates of EGs. The protein truncation, which is pH and temperature dependent, occurred between amino acids 315 and 316, but removal of these two amino acids did not stop the process. Furthermore, mutations of E142A and E231A, which are essential for EG activity, did not affect the protein self-truncation process. Conversely, two single amino acid substitution mutations affected the self-truncation activity without much impact on EG activities. In Geobacillus sp. 70PC53, the full-length GsCelA was first synthesized in the cell but progressively transformed into the truncated form and eventually secreted. The GsCelA self-truncation was not affected by standard protease inhibitors, but could be suppressed by EDTA and EGTA and enhanced by certain divalent ions, such as Ca²⁺, Mg²⁺, and Cu²⁺.

Conclusions

This study reveals novel insights into the strategy of Gram-positive bacteria for directing their GH5 EGs to the substrate, and then releasing the catalytic part for enhanced activity via a spontaneous self-truncation process.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01334-y.

A proteomics strategy for the identification of multiple sites in sulfur mustard-modified HSA and screening potential biomarkers for retrospective analysis of exposed human plasma

A major challenge for the unequivocal verification of alleged exposure to sulfur mustard (HD) lies in identifying its multiple modifications on endogenous proteins and utilizing these modified proteins to achieve accurate, sensitive, and rapid detection for retrospective analysis of HD exposure. As the most abundant protein in human plasma, human serum albumin (HSA) can react with many xenobiotics, such as HD, to protect the body from damage. The HSA adducts induced by HD have been used as biomarkers for the verification of HD exposure. In this study, the modification sites on HSA by HD were identified through application of the bottom-up strategy used in proteomics, and 41 modified sites were discovered with seven types of amino acids, of which 3 types were not previously reported. Then, different enzymes, including pepsin, endoproteinase Glu-C, and pronase, were applied to digest HD-HSA to produce adducts with hydroxyethylthioethyl (HETE) groups, which may be used as potential biomarkers for HD exposure. As candidates for retrospective analysis, sixteen adducts were obtained and characterized with ultra-high-pressure liquid chromatography coupled with quadrupole-Orbitrap mass spectrometry (UHPLC-QE Focus MS). These potential biomarkers were evaluated in human plasma that was exposed in vitro to HD and five of its analogues. This study integrated the identification of modification sites through application of the bottom-up strategy of proteomics and screening biomarkers, providing a novel strategy for retrospective detection of the exposure of xenobiotic chemicals.

Generation of a Library of Carbohydrate-Active Enzymes for Plant Biomass Deconstruction

In nature, the deconstruction of plant carbohydrates is carried out by carbohydrate-active enzymes (CAZymes). A high-throughput (HTP) strategy was used to isolate and clone 1476 genes obtained from a diverse library of recombinant CAZymes covering a variety of sequence-based families, enzyme classes, and source organisms. All genes were successfully isolated by either PCR (61%) or gene synthesis (GS) (39%) and were subsequently cloned into Escherichia coli expression vectors. Most proteins (79%) were obtained at a good yield during recombinant expression. A significantly lower number (p < 0.01) of proteins from eukaryotic (57.7%) and archaeal (53.3%) origin were soluble compared to bacteria (79.7%). Genes obtained by GS gave a significantly lower number (p = 0.04) of soluble proteins while the green fluorescent protein tag improved protein solubility (p = 0.05). Finally, a relationship between the amino acid composition and protein solubility was observed. Thus, a lower percentage of non-polar and higher percentage of negatively charged amino acids in a protein may be a good predictor for higher protein solubility in E. coli. The HTP approach presented here is a powerful tool for producing recombinant CAZymes that can be used for future studies of plant cell wall degradation. Successful production and expression of soluble recombinant proteins at a high rate opens new possibilities for the high-throughput production of targets from limitless sources.

SARS-CoV-2 infection in the mouse olfactory system

SARS-CoV-2 infection causes a wide spectrum of clinical manifestations in humans, and olfactory dysfunction is one of the most predictive and common symptoms in COVID-19 patients. However, the underlying mechanism by which SARS-CoV-2 infection leads to olfactory disorders remains elusive. Herein, we demonstrate that intranasal inoculation with SARS-CoV-2 induces robust viral replication in the olfactory epithelium (OE), not the olfactory bulb (OB), resulting in transient olfactory dysfunction in humanized ACE2 (hACE2) mice. The sustentacular cells and Bowman’s gland cells in the OE were identified as the major target cells of SARS-CoV-2 before invasion into olfactory sensory neurons (OSNs). Remarkably, SARS-CoV-2 infection triggers massive cell death and immune cell infiltration and directly impairs the uniformity of the OE structure. Combined transcriptomic and quantitative proteomic analyses revealed the induction of antiviral and inflammatory responses, as well as the downregulation of olfactory receptor (OR) genes in the OE from the infected animals. Overall, our mouse model recapitulates olfactory dysfunction in COVID-19 patients and provides critical clues for understanding the physiological basis for extrapulmonary manifestations of COVID-19.

Proteogenomics Study of Blastobotrys adeninivorans TMCC 70007-A Dominant Yeast in the Fermentation Process of Pu-erh Tea

Blastobotrys adeninivorans plays an essential role in pile-fermenting of Pu-erh tea. Its ability to assimilate various carbon and nitrogen sources makes it available for application in a wide range of industry sectors. The genome of B. adeninivorans TMCC 70007 isolated from pile-fermented Pu-erh tea was sequenced and assembled. Proteomics analysis indicated that 4900 proteins in TMCC 70007 were expressed under various culture conditions. Proteogenomics mapping revealed 48 previously unknown genes and corrected 118 gene models predicted by GeneMark-ES. Ortho-proteogenomics analysis identified 17 previously unidentified genes in B. adeninivorans LS3, the first strain with a sequenced genome among the genus Blastobotrys as well. More importantly, five species specific genes were identified from TMCC 70007, which could serve as a barcode for strain typing and were applicable for fermentation process protection of this industrial species. The datasets generated from tea aqueous extract culture not only increased the proteome coverage and accuracy but also contributed to the identification of proteins related to polyphenols and caffeine, which were considered to change greatly during the microbial fermentation of Pu-erh tea. This study provides a proteome perspective on TMCC 70007, which was considered to be an important strain in the production of Pu-erh tea. The systematic proteogenomics analysis not only made a better annotation on the genome of B. adeninivorans TMCC 70007 as previous proteogenomics study but also provided solution for fermentation process protection on valuable industrial species with species specific genes uniquely identified from proteogenomics study.

Unambiguous Phosphosite Localization through the Combination of Trypsin and LysargiNase Mirror Spectra in a Large-Scale Phosphoproteome Study

Understanding of the kinase-guided signaling pathways requires the identification and analysis of phosphosites. Mass spectrometry (MS)-based phosphoproteomics is a rapid and highly sensitive approach for high-throughput identification of phosphosites. However, phosphosite determination from MS data with a single protease is more likely to be ambiguous, regardless of the strategy used for phosphopeptide detection. Here, we explored the application of LysargiNase, which was recently reported to mirror trypsin in specificity to cleave arginine and lysine residues exclusively at the N-terminal side. We found that the combination of trypsin and LysargiNase mirror spectra resulted in higher ion coverage in MS₂ spectra. The median ion coverage values of b ions in tryptic spectra, LysargiNase spectra, and combined spectra are 8.3, 20.5, and 25.0%, respectively. As for the median ion coverage of y ions, these values are 27.8, 10.0, and 32.3%. Higher ion coverage was helpful to pinpoint the precise phosphosites. Compared to trypsin alone, the combined use of trypsin and LysargiNase mirror spectra enabled 67.1% of mirror spectra with unreliable scores (confidence score <0.75) to become reliable (confidence score ≥ 0.75). Meanwhile, all of the mirror peptide-spectrum matches (PSMs) with multiple potential phosphosites from trypsin and LysargiNase digests could be assigned one precise phosphosite after applying the combination strategy. Besides, the combination strategy could identify more novel phosphosites than the union strategy did. We synthesized three phosphopeptides corresponding to the three novel phosphosites and validated the reliability of the identification. Taken together, our data demonstrated the distinctive potential of the combination strategy presented here for unambiguous phosphosite localization (Project accession PXD011178).

Quantitative Proteomics Reveals the Development of HBV-Associated Glomerulonephritis Triggered by the Downregulation of SLC7A7

As a hepadnavirus, hepatitis B virus (HBV) can cause damage to extrahepatic organs. The kidney is one of the organs that is more susceptible to damage. Research studies on HBV-associated glomerulonephritis (HBV-GN) have been going on for decades. However, the underlying molecular mechanism remains obscure. Here, we applied a tandem mass tag (TMT) isobaric labeling-based method to quantitatively profile the kidney proteome of HBV transgenic mice to illustrate the pathological mechanisms of HBV-GN. Weighted correlation network analysis, a clustering method for gene expression, is used to cluster proteins. Totally, we identified 127 proteins that were highly associated with HBV expression out of a total of 5169 quantified proteins. Among them, the downregulated solute carrier (SLC) family proteins are involved in the process of HBV-GN. We also found that IL1B was upregulated in the kidney tissue of HBV transgenic mice. These findings suggest that HBV disrupts the small molecule transport network of the kidney, which contributes to the occurrence of HBV-GN. The transporter, particularly SLC family 7 member 7 (SLC7A7), is involved in this process, which might serve as an intervention target for HBV-GN. All MS data have been deposited to the ProteomeXchange Consortium via the iProX partner repository with the data set identifier PXD016450.

Recombinant expression, purification and characterization of acetylated LysargiNase from Escherichia coli with high activity and stability

RATIONALE

LysargiNase is a novel characterized metalloprotease that can cleave the N-terminii of lysine or arginine residues. The peptides generated by LysargiNase are just mirrors to those generated by trypsin. These characteristics of LysargiNase provide a powerful tool for mass spectrometry (MS)-based proteomics research. A highly active and stable LysargiNase produced by an easy and inexpensive method could greatly benefit proteomics research. Here, we report the soluble recombinant expression, purification and acetyl modification of LysargiNase in Escherichia coli.

METHODS

The coding sequence of LysargiNase with an enterokinase cleavage site at the N-terminus was inserted into plasmid pGEX-4 T-2 and transformed into E. coli BL21 (DE3). The strain was cultured in a 14-L fermenter with a working volume of 5 L. The protein expression was induced by adding isopropyl-β-D-thiogalactoside (IPTG) to a final concentration of 1 mM. The recombinant LysargiNase was loaded onto a GSTrap and an on-column digestion was performed to remove the GST tag and was subsequently purified by chromatographic purification. In vitro acetylation of LysargiNase was performed by using acetic anhydride. The digestion efficiency and specificity of recombinant LysargiNase and acetylated LysargiNase were compared with simple protein substrate, human serum albumin (HSA), and a complex proteomic sample, yeast lysate, by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography/tandem mass spectrometry (LC/MS/MS).

RESULTS

Highly soluble expression of recombinant LysargiNase was achieved by plasmid pGEX-4 T-2 in E. coli BL21 (DE3). In addition, acetylation of purified LysargiNase significantly increased its resistance to autolysis, which resulted in a more complete digestion of proteomics samples and more identified peptides and proteins by LC/MS/MS.

CONCLUSIONS

In this study, we constructed a highly soluble expression system for producing recombinant LysargiNase in E. coli, which gave tremendous advantages in the downstream purification process. We also confirmed that acetyl modification can increase the stability and activity of recombinant LysargiNase. The study provided a superior way to produce this powerful tool for proteomics research.

Precision De Novo Peptide Sequencing Using Mirror Proteases of Ac-LysargiNase and Trypsin for Large-scale Proteomics

De novo peptide sequencing for large-scale proteomics remains challenging because of the lack of full coverage of ion series in tandem mass spectra. We developed a mirror protease of trypsin, acetylated LysargiNase (Ac-LysargiNase), with superior activity and stability. The mirror spectrum pairs derived from the Ac-LysargiNase and trypsin treated samples can generate full b and y ion series, which provide mutual complementarity of each other, and allow us to develop a novel algorithm, pNovoM, for de novo sequencing. Using pNovoM to sequence peptides of purified proteins, the accuracy of the sequence was close to 100%. More importantly, from a large-scale yeast proteome sample digested with trypsin and Ac-LysargiNase individually, 48% of all tandem mass spectra formed mirror spectrum pairs, 97% of which contained full coverage of ion series, resulting in precision de novo sequencing of full-length peptides by pNovoM. This enabled pNovoM to successfully sequence 21,249 peptides from 3,753 proteins and interpreted 44-152% more spectra than pNovo+ and PEAKS at a 5% FDR at the spectrum level. Moreover, the mirror protease strategy had an obvious advantage in sequencing long peptides. We believe that the combination of mirror protease strategy and pNovoM will be an effective approach for precision de novo sequencing on both single proteins and proteome samples.

Multiproteases Combined with High-pH Reverse-Phase Separation Strategy Verified Fourteen Missing Proteins in Human Testis Tissue

Subsequent to conducting the Chromosome-Centric Human Proteome Project, we have focused on human testis-enriched missing proteins (MPs) since 2015. For protein coverage to be enhanced, a multiprotease strategy was used for separation of samples by 10% SDS-PAGE. For the separating efficiency to be improved, a high-pH reverse phase (RP) separation strategy was applied to fractionate complex samples in this study. A total of 11,558 proteins was identified, which is the largest proteome data set for single human tissue sample so far. On the basis of this large-scale data set, we verified 14 MPs (PE2) in neXtProt (2018-01) after spectrum quality analysis, isobaric post-translational modification, and single amino acid variant filtering, and synthesized peptide matching. Tissue expression analysis showed that 3 of 14 MPs were testis-specific proteins. Functional analysis showed that 10 of 14 MPs were closely related to liver tumor, liver carcinoma, and hepatocellular carcinoma. Another 100 MPs were listed as candidates but required additional verification information. All MS data sets have been deposited into the ProteomeXchange with the identifier PXD009737.

iTRAQ-Based Membrane Proteomics Reveals Plasma Membrane Proteins Change During HepaRG Cell Differentiation

HepaRG cell, a stabilized bipotent liver progenitor cell line, exhibits hepatocyte functions only after differentiation. However, the mechanism of transition from nondifferentiated to differentiated states, accompanied by proliferation migration and differentiation, remains poorly understood, particularly those proteins residing in the plasma membrane. In this study, the membrane protein expression change of HepaRG cell during differentiation were systematically analyzed using an iTRAQ labeled quantitative membrane proteomics approach. A total of 70 membrane proteins were identified to be differentially expressed among 849 quantified membrane proteins. Function and disease clustering analysis proved that 11 of these proteins are involved in proliferation, migration, and differentiation. Two key factors (MMP-14 and OCLN) were validated by qRT-PCR and Western blot. Blockade of MMP-14 further demonstrated its important function during tumor cell migration. The data sets have been uploaded to ProteomeXchange with the identifier PXD004752.

Searching Missing Proteins Based on the Optimization of Membrane Protein Enrichment and Digestion Process

A membrane protein enrichment method composed of ultracentrifugation and detergent-based extraction was first developed based on MCF7 cell line. Then, in-solution digestion with detergents and eFASP (enhanced filter-aided sample preparation) with detergents were compared with the time-consuming in-gel digestion method. Among the in-solution digestion strategies, the eFASP combined with RapiGest identified 1125 membrane proteins. Similarly, the eFASP combined with sodium deoxycholate identified 1069 membrane proteins; however, the in-gel digestion characterized 1091 membrane proteins. Totally, with the five digestion methods, 1390 membrane proteins were identified with ≥1 unique peptides, among which 1345 membrane proteins contain unique peptides ≥2. This is the biggest membrane protein data set for MCF7 cell line and even breast cancer tissue samples. Interestingly, we identified 13 unique peptides belonging to 8 missing proteins (MPs). Finally, eight unique peptides were validated by synthesized peptides. Two proteins were confirmed as MPs, and another two proteins were candidate detections.

Recombinant expression, refolding, purification and characterization of Pseudomonas aeruginosa protease IV in Escherichia coli

Several protease IV enzymes are widely used in proteomic research. Specifically, protease IV from Pseudomonas aeruginosa has lysyl endopeptidase activity. Here, we report the recombinant expression, refolding, activation, and purification of this protease in Escherichia coli. Proteolytic instability of the activated intermediate, a major obstacle for efficient production, is controlled through ammonium sulfate precipitation. The purified protease IV exhibits superior lysyl endopeptidase activity compared to a commercial product.

Recombinant acetylated trypsin demonstrates superior stability and higher activity than commercial products in quantitative proteomics studies

RATIONALE

Trypsin is an important digestive enzyme in peptide sample preparation for proteomics. It digests proteins at the C-terminal of Arg or Lys residues. The majority of commercial products are obtained from animal sources. In a previous study, we reported the production process for recombinant trypsin (r-trypsin) and acetylated trypsin (r-Ac-trypsin). In this paper, we want to evaluate whether the r-trypsin and r-Ac-trypsin are suitable for proteomics research.

METHODS

The trypsins used in this research were first normalized to the same concentration and used for further evaluation. The stability and buffer compatibility (2M urea, 0.1% SDS and 10% acetonitrile) were compared and visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The digestion efficiency and specificity were compared based on a simple protein substrate, human serum albumin (HSA) and a complex proteomic sample, yeast lysate. The acquisition of proteomics data was achieved by ultra-high performance liquid chromatography (UPLC) connected to an LTQ Orbitrap Velos mass spectrometer.

RESULTS

r-Ac-trypsin demonstrated similar tolerance to 2 M urea and 10% acetonitrile but weaker 0.1% SDS tolerance than commercial trypsins. Based on simple protein sample HSA, the activity and specificity of r-Ac-trypsin were similar to that of commercial trypsins. However, it demonstrated superior activity and specificity on complicated samples like yeast lysate. More interestingly, the newly developed r-Ac-trypsin was more resistant to autolysis, which enabled more complete digestion of proteomic samples.

CONCLUSIONS

The r-Ac-trypsin described here is a recombinant product. In addition it showed similar or superior properties such as stability activity and specificity to commercial products. It can be used in peptide sample preparation in proteomics studies.

Improved Production of Active Streptomyces griseus Trypsin with a Novel Auto-Catalyzed Strategy

N-terminal sequences play crucial roles in regulating expression, translation, activation and enzymatic properties of proteins. To reduce cell toxicity of intracellular trypsin and increase secretory expression, we developed a novel auto-catalyzed strategy to produce recombinant trypsin by engineering the N-terminus of mature Streptomyces griseus trypsin (SGT). The engineered N-terminal peptide of SGT was composed of the thioredoxin, glycine-serine linker, His₆-tag and the partial bovine trypsinogen pro-peptide (DDDDK). Furthermore, we constructed a variant TLEI with insertion of the artificial peptide at N-terminus and site-directed mutagenesis of the autolysis residue R145. In fed-batch fermentation, the production of extracellular trypsin activity was significantly improved to 47.4 ± 1.2 U·ml⁻¹ (amidase activity, 8532 ± 142.2 U·ml⁻¹ BAEE activity) with a productivity of 0.49 U·ml⁻¹·h⁻¹, which was 329% greater than that of parent strain Pichia pastoris GS115-SGT. This work has significant potential to be scaled-up for microbial production of SGT. In addition, the N-terminal peptide engineering strategy can be extended to improve heterologous expression of other toxic enzymes.