Microbial serine protease inhibitors and their therapeutic applications

The proteolytic activity in inflammatory bowel disease: insight from gut microbiota

Inflammatory bowel disease (IBD) is a chronic, recurrent inflammatory disease caused by the destruction of the intestinal mucosal epithelium that affects a growing number of people worldwide. Although the etiology of IBD is complex and still elucidated, the role of dysbiosis and dysregulated proteolysis is well recognized. Various studies observed altered composition and diversity of gut microbiota, as well as increased proteolytic activity (PA) in serum, plasma, colonic mucosa, and fecal supernatant of IBD compared to healthy individuals. The imbalance of intestinal microecology and intestinal protein hydrolysis were gradually considered to be closely related to IBD. Notably, the pivotal role of intestinal microbiota in maintaining proteolytic balance received increasing attention. In summary, we have speculated a mesmerizing story, regarding the hidden role of PA and microbiota-derived PA hidden in IBD. Most importantly, we provided the diagnosis and therapeutic targets for IBD as well as the formulation of new treatment strategies for other digestive diseases and protease-related diseases.

A Novel Kunitz-Type Serine Protease Inhibitor (HcKuSPI) is Involved in Antibacterial Defense in Innate Immunity and Participates in Shell Formation of Hyriopsis cumingii

Serine protease inhibitors (SPIs) are abundantly reported for its inhibition against specific proteases involved in the immune responses, but SPI data related to calcareous shells are scarce. Previously, our research group has reported the proteome analysis of non-nucleated pearl powder, and a candidate matrix protein containing two Kunitz domains in the acid soluble fraction caught our attention. In the present study, the full-length cDNA sequence of HcKuSPI was obtained from Hyriopsis cumingii. HcKuSPI was specifically expressed in the mantle, with hybridization signals mainly concentrated to dorsal epithelial cells at the mantle edge and weak signals at the mantle pallium, suggesting HcKuSPI was involved in shell formation. HcKuSPI expression in the mantle was upregulated after Aeromonas hydrophila and Staphylococcus aureus challenge to extrapallial fluids (EPFs). A glutathione S transferase (GST)-HcKuSPI recombinant protein showed strong inhibitory activity against the proteases, trypsin and chymotrypsin. Moreover, HcKuSPI expression in an experimental group was significantly higher when compared with a control group during pellicle growth and crystal deposition in shell regeneration processes, while the organic shell framework of newborn prisms and nacre tablets was completely destroyed after HcKuSPI RNA interference (RNAi). Therefore, HcKuSPI secreted by the mantle may effectively neutralize excess proteases and bacterial proteases in the EPF during bacterial infection and could prevent matrix protein extracellular degradation by suppressing protease proteolytic activity, thereby ensuring a smooth shell biomineralization. In addition, GST-HcKuSPI was also crucial for crystal morphology regulation. These results have important implications for our understanding of the potential roles of SPIs during shell biomineralization.

Regulation of human neutrophil IL-1β secretion induced by Escherichia coli O157:H7 responsible for hemolytic uremic syndrome

Shiga-toxin producing Escherichia coli (STEC) infections can cause from bloody diarrhea to Hemolytic Uremic Syndrome. The STEC intestinal infection triggers an inflammatory response that can facilitate the development of a systemic disease. We report here that neutrophils might contribute to this inflammatory response by secreting Interleukin 1 beta (IL-1β). STEC stimulated neutrophils to release elevated levels of IL-1β through a mechanism that involved the activation of caspase-1 driven by the NLRP3-inflammasome and neutrophil serine proteases (NSPs). Noteworthy, IL-1β secretion was higher at lower multiplicities of infection. This secretory profile modulated by the bacteria:neutrophil ratio, was the consequence of a regulatory mechanism that reduced IL-1β secretion the higher were the levels of activation of both caspase-1 and NSPs, and the production of NADPH oxidase-dependent reactive oxygen species. Finally, we also found that inhibition of NSPs significantly reduced STEC-triggered IL-1β secretion without modulating the ability of neutrophils to kill the bacteria, suggesting NSPs might represent pharmacological targets to be evaluated to limit the STEC-induced intestinal inflammation.

A secreted BPTI/Kunitz inhibitor domain-containing protein of barber's pole worm interacts with host NLRP3 inflammasome activation-associated G protein subunit to inhibit IL-1β and IL-18 maturation in vitro

Protease inhibitors are major components of excretory/secretory products released by parasitic nematodes and have been proposed to play roles in host-parasite interactions. Haemonchus contortus (the barber's pole worm) encodes for several serine protease inhibitors, and in a previous study we identified a trypsin inhibitor-like serine protease inhibitor of this blood-feeding nematode, SPI-I8, as necessary for anticoagulation. Here, we demonstrated that a bovine pancreatic trypsin inhibitor/Kunitz-type serine protease inhibitor (BPTI/Kunitz) domain-containing protein highly expressed in parasitic stages, HCON_00133150, is involved in suppressing proinflammatory cytokine production in mammalian cells. Fluorescent labelling of HCON_00133150 revealed a punctate localisation at the inner hypodermal membrane of H. contortus, an organ closely related to the excretory column. Yeast two-hybrid screening and immunoprecipitation-mass spectrometry identified that the recombinant HCON_00133150 physically interacted with a range of host proteins including the G protein subunit beta 1 of sheep (Ovis aries; OaGNB1), a negative regulator of NLRP3 inflammasome activation. Interestingly, heterologous expression of HCON_00133150 enhanced the inhibitory effect of OaGNB1 on NLRP3 inflammasome and the maturation of proinflammatory cytokines IL-1β and IL-18 in transfected cells. 1-to-1 orthologues (n = 33) of BPTI/Kunitz inhibitor domain-containing proteins were predicted in clades III, IV and V (but not clade I) parasitic nematodes. Structural (tandem BPTI/Kunitz inhibitor domains inverted into the globular reticulation) and functional (a GNB1 enhancer) characterisation of HCON_00133150 and its orthologues elucidated that these molecules might contribute to immune suppression by parasitic nematodes in animals and humans.

Polymer-lipid hybrid nanoparticles as potential lipophilic anticancer drug carriers

Nanocarrier systems are widely used for drug delivery applications, but limitations such as the use of synthetic surfactants, leakage of toxic drugs, and a poor encapsulation capacity remain as challenges. We present a new hybrid nanocarrier system that utilizes natural materials to overcome these limitations and improve the safety and efficacy of drug delivery. The system comprises a biopolymeric shell and a lipid core, encapsulating the lipophilic anticancer drug paclitaxel. Bovine serum albumin and dextran, in various molecular weights, are covalently conjugated via Maillard reaction to form the shell which serves as a stabilizer to maintain nanoparticle integrity. The properties of the system, such as Maillard conjugate concentration, protein/polysaccharide molar ratio, and polysaccharide molecular weight, are optimized to enhance nanoparticle size and stability. The system shows high stability at different pH conditions, high drug loading capacity, and effective in vitro drug release through the trigger of enzymes and passive diffusion. Serine proteases are used to digest the protein portion of the nanoparticle shell to enhance the drug release. This nanocarrier system represents a significant advancement in the field of nanomedicine, offering a safe and effective alternative for the delivery of lipophilic drugs.

Gene cloning and functional study of PmKSPI from Pinctada fucata martensii

Kunitz-type serine protease inhibitors (KSPI) are a family of serine protease inhibitors (SPIs) and are extensively found in animals, plants, and microbes. SPI can inhibit proteases that may be harmful or unwanted to its cells. Here, a four-domain Kunitz-type SPI, PmKSPI, was cloned by RACE in the pearl oyster Pinctada fucata martensii. The full-length cDNA sequence of PmKSPI was 1318 bp, including the 5' UTR (25 bp), the 3' UTR (96 bp) and ORF (1197 bp). Homology analysis indicated that PmKSPI had the highest resemblance (30.14%) with its homolog in Crassostrea gigas. Phylogenetic analysis revealed that PmKSPI clustered with homologs in other molluscs. We found that PmKSPI mRNA expression in P. f. martensii was distributed in all six tissues, with the highest level in the mantle, and almost no expression in other tissues. After PAMPs challenge, expression of PmKSPI mRNA in the mantle was significantly up-regulated. The recombinant protein rPmKSPI significantly inhibited the growth of 5 kinds of Gram-negative bacteria but had little effect on Gram-positive bacterial activity. Transmission electron microscopy showed that plasmolysis occurred in two Gram-negative bacteria species when treated with rPmKSPI. rPmKSPI may thus have a bactericidal effect by destroying the bacterial cell membrane or cell walls and releasing its contents. Therefore, our results suggest that PmKSPI is tightly associated with the immunological defence of P. f. martensii.

Integrated RNA-seq and RNAi Analysis of the Roles of the Hsp70 and SP Genes in Red-Shell Meretrix meretrix Tolerance to the Pathogen Vibrio parahaemolyticus

The "Wanlihong" Meretrix meretrix (WLH-M) clam is a new variety of this species that has a red shell and stronger Vibrio tolerance than ordinary M. meretrix (ORI-M). To investigate the molecular mechanisms responsible for the WLH-M strain's tolerance to Vibrio, we challenged clams with Vibrio parahaemolyticus and then assessed physiological indexes and conducted transcriptome analysis and RNA interference experiments. The mortality, tissue bacterial load, and hemocyte reactive oxygen species level of ORI-M were significantly higher than those of WLH-M, whereas the content and activity of lysozyme were significantly lower. Gene Ontology functional annotation analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that immune and metabolic pathways were enriched in Vibrio-challenged clams. The expressions of the heat shock protein 70 (Hsp70) and serine protease (SP) genes, which are involved in antibacterial immunity, were significantly upregulated in WLH-M but not in ORI-M, while the expression of the kynurenine 3-monooxygenase gene, a proinflammatory factor, was significantly downregulated in WLH-M. RNA interference experiments confirmed that Hsp70 and SP downregulation could result in increased mortality of WLH-M. Therefore, we speculate that Hsp70 and SP may be involved in the antibacterial immunity of WLH-M in vivo. Our data provided a valuable resource for further studies of the antibacterial mechanism of WLH-M and provided a foundation for the breeding of pathogen-resistant strains.

Genetic engineering for enhanced production of a novel alkaline protease BSP-1 in Bacillus amyloliquefaciens

Alkaline protease has been widely applied in food, medicine, environmental protection and other industrial fields. However, the current activity and yield of alkaline protease cannot meet the demand. Therefore, it is important to identify new alkaline proteases with high activity. In this study, we cloned a potential alkaline protease gene bsp-1 from a Bacillus subtilis strain isolated in our laboratory. BSP-1 shows the highest sequence similarity to subtilisin NAT (S51909) from B. subtilis natto. Then, we expressed BSP-1 in Bacillus amyloliquefaciens BAX-9 and analyzed the protein expression level under a collection of promoters. The results show that the P43 promoter resulted in the highest transcription level, protein level and enzyme activity. Finally, we obtained a maximum activity of 524.12 U/mL using the P43 promoter after fermentation medium optimization. In conclusion, this study identified an alkaline protease gene bsp-1 from B. subtilis and provided a new method for high-efficiency alkaline protease expression in B. amyloliquefaciens.

Isolation, identification, and whole-genome sequencing of high-yield protease bacteria from Daqu of ZhangGong Laojiu

A total of 296 strains of protease-producing bacteria were isolated and purified from medium-temperature Daqu produced by ZhangGong LaoJiu Wine Co. Ltd. After calculating the ratio of transparent ring diameter to colony diameter and measuring the protease activities, a strain of high-yield protease bacteria, called DW-7, was screened out with a protease activity of 99.54 U/mL. Through morphological observation, 16S rDNA sequence analysis, and physiological and biochemical tests, the isolated bacteria DW-7 was determined to be Bacillus velezensis. In addition, whole-genome sequencing (WGS), using PacBio and the Illumina platform, was performed. Gene annotation was then conducted using the Clusters of Orthologous Groups (COG), Kyoto Encyclopedia of Genes and Genomes (KEGG), Non-Redundant Protein Sequence Database (NR), and Gene Ontology (GO) databases. The results showed that the genome of DW-7 was 3,942,829 bp long with a GC content of 46.45%. A total of 3,662 protein-encoding genes were predicted, with a total length of 3,402,822 bp. Additionally, 2,283; 2,796; and 2,127 genes were annotated in the COG, KEGG, and GO databases, respectively. A total of 196 high-yield protease genes were mainly enriched in the metabolism of alanine, aspartic acid, glutamate, glycine, serine, and threonine, as well as ABC transporter and transporter pathways.

Protease Inhibitors from Plants as Therapeutic Agents- A Review

Plant-based diets are a great source of protease inhibitors (PIs). Two of the most well-known families of PIs are Bowman-Birk inhibitors (BBI) and Kunitz-type inhibitors (KTI). The first group acts mainly on trypsin, chymotrypsin, and elastase; the second is on serine, cysteine, and aspartic proteases. PIs can retard or inhibit the catalytic action of enzymes; therefore, they are considered non-nutritional compounds; nevertheless, animal studies and cell line experiments showed promising results of PIs in treating human illnesses such as obesity, cardiovascular diseases, autoimmune diseases, inflammatory processes, and different types of cancer (gastric, colorectal, breast, and lung cancer). Anticarcinogenic activity's proposed mechanisms of action comprise several inhibitory effects at different molecular levels, i.e., transcription, post-transcription, translation, post-translation, and secretion of cancer cells. This work reviews the potential therapeutic applications of PIs as anticarcinogenic and anti-inflammatory agents in human diseases and the mechanisms by which they exert these effects.

Proteins from the core genome of Corynebacterium ulcerans respond for pathogenicity and reveal promising vaccine targets for diphtheria

Corynebacterium ulcerans is an emerging pathogen able to transmit the acute infection diphtheria to humans. Although there is a well-established vaccine based on the toxin produced by Corynebacterium diphtheriae, another species of this genus known to cause the disease, there is still no vaccine formulations described for C. ulcerans; this fact contributes to the increase in cases of infection that has been observed. In this study, we want to provide information at the genomic level of this bacterium in order to suggest proteins as possible vaccine targets. We carried out an in silico prospection of vaccine candidates through reverse vaccinology for targets that exhibit antigenic potential against diphtheria. We found important virulence factors, such as adhesion-related ones, that are responsible for pathogen-host interaction after infection, but we did not find the diphtheria toxin, which is the main component of the currently available vaccine. This study provides detailed information about the exoproteome and hypothetical proteins from the core genome of C. ulcerans, suggesting vaccine targets to be further tested in vitro for the development of a new vaccine against diphtheria.

Structural and functional analysis of broad pH and thermal stable protease from Penicillium aurantiogriseum URM 4622

This study aimed to better characterize a recently purified stable extracellular alkaline peptidase produced by Penicillium aurantiogriseum (URM 4622) through fluorescence spectroscopy, far-UV circular dichroism, kinetic and thermodynamic models to understand its' structure-activity and denaturation. Fluorescence data showed that changing pH leads to tryptophan residues exposure to more hydrophilic environments at optimum activity pH 9.0 and 10.0. When thermally treated, it displayed less unfolding at these pH values, along with 4-fold less photoproducts formation than at neutral pH. Different pH CD spectra showed more β-sheet (21.5-43.0%) than α-helix (1-6.2%). At pH9.0, more than 2-fold higher α-helix content than any other pH. The melting temperature (T_m) was observed between 50 and 60 °C at all pH studied, with lower T_m at pH 9.0-11.0 (54.9-50.3 °C). The protease displayed two phase transition, with two energies of denaturation, and a 4-fold higher thermal stability (ΔH°_m) than reports for other microorganism's proteases. An irreversible folding transition occurs between 50 and 60 °C. It displayed energies of denaturation suggesting higher thermal stability than reported for other microorganism's proteases. These results help elucidating the applicability of this new stable protease.

Gut Serpinome: Emerging Evidence in IBD

Inflammatory bowel diseases (IBD) are incurable disorders whose prevalence and global socioeconomic impact are increasing. While the role of host genetics and immunity is well documented, that of gut microbiota dysbiosis is increasingly being studied. However, the molecular basis of the dialogue between the gut microbiota and the host remains poorly understood. Increased activity of serine proteases is demonstrated in IBD patients and may contribute to the onset and the maintenance of the disease. The intestinal proteolytic balance is the result of an equilibrium between the proteases and their corresponding inhibitors. Interestingly, the serine protease inhibitors (serpins) encoded by the host are well reported; in contrast, those from the gut microbiota remain poorly studied. In this review, we provide a concise analysis of the roles of serine protease in IBD physiopathology and we focus on the serpins from the gut microbiota (gut serpinome) and their relevance as a promising therapeutic approach.

The relationship between gut microbiota and proteolytic activity in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disease that affects 3.8-9.2% of the world population. It affects the physiology and psychology of patients and increases the burden on families, the healthcare system, society, and economic development. Presently, a large number of studies have shown that compared to healthy individuals, the composition and diversity of gut microbiota in IBS patients have changed, and the proteolytic activity (PA) in fecal supernatant and colonic mucosa of IBS patients has also increased. These findings indicate that the imbalance of intestinal microecology and intestinal protein hydrolysis is closely related to IBS. Furthermore, the intestinal flora is a key substance that regulates the PA and is associated with IBS. The current review described the intestinal microecology and intestinal proteolytic activity of patients with IBS and also discussed the effect of intestinal flora on PA. In summary, this study proposed a pivotal role of gut microbiota and PA in IBS, respectively, and provided an in-depth insight into the diagnosis and treatment targets of IBS as well as the formulation of new treatment strategies for other digestive diseases and protease-related diseases.

Digestive Inflammation: Role of Proteolytic Dysregulation

Dysregulation of the proteolytic balance is often associated with diseases. Serine proteases and matrix metalloproteases are involved in a multitude of biological processes and notably in the inflammatory response. Within the framework of digestive inflammation, several studies have stressed the role of serine proteases and matrix metalloproteases (MMPs) as key actors in its pathogenesis and pointed to the unbalance between these proteases and their respective inhibitors. Substantial efforts have been made in developing new inhibitors, some of which have reached clinical trial phases, notwithstanding that unwanted side effects remain a major issue. However, studies on the proteolytic imbalance and inhibitors conception are directed toward host serine/MMPs proteases revealing a hitherto overlooked factor, the potential contribution of their bacterial counterpart. In this review, we highlight the role of proteolytic imbalance in human digestive inflammation focusing on serine proteases and MMPs and their respective inhibitors considering both host and bacterial origin.

Insights into the Role of Tick Salivary Protease Inhibitors during Ectoparasite-Host Crosstalk

Protease inhibitors (PIs) are ubiquitous regulatory proteins present in all kingdoms. They play crucial tasks in controlling biological processes directed by proteases which, if not tightly regulated, can damage the host organism. PIs can be classified according to their targeted proteases or their mechanism of action. The functions of many PIs have now been characterized and are showing clinical relevance for the treatment of human diseases such as arthritis, hepatitis, cancer, AIDS, and cardiovascular diseases, amongst others. Other PIs have potential use in agriculture as insecticides, anti-fungal, and antibacterial agents. PIs from tick salivary glands are special due to their pharmacological properties and their high specificity, selectivity, and affinity to their target proteases at the tick-host interface. In this review, we discuss the structure and function of PIs in general and those PI superfamilies abundant in tick salivary glands to illustrate their possible practical applications. In doing so, we describe tick salivary PIs that are showing promise as drug candidates, highlighting the most promising ones tested in vivo and which are now progressing to preclinical and clinical trials.

A critical review on marine serine protease and its inhibitors: A new wave of drugs?

Marine organisms are rich sources of enzymes and their inhibitors having enormous therapeutic potential. Among different proteolytic enzymes, serine proteases, which can be obtained from various marine organisms show a potential to biomedical application as thrombolytic agents. Although this type of proteases plays a crucial role in almost all biological processes, their uncontrolled activity often leads to several diseases. Accordingly, the actions of these types of proteases are regulated by serine protease inhibitors (SPIs). Marine SPIs control complement activation and various other physiological functions, such as inflammation, immune function, fibrinolysis, blood clotting, and cancer metastasis. This review highlights the potential use of serine proteases and their inhibitors as the new wave of promising drugs.

Enzymes for pharmaceutical and therapeutic applications

Enzymes are highly efficient and selective biocatalysts, present in the living beings. They exist in enormous varieties in terms of the types of reactions catalyzed by them for instance oxidation-reduction, group transfers within the molecules or between the molecules, hydrolysis, isomerization, ligation, bond cleavage, and bond formation. Besides, enzyme based catalyses are performed with much higher fidelity, under mild reaction conditions and are highly efficient in terms of number of steps, giving them an edge over their chemical counter parts. The unique characteristics of enzymes makes them highly applicable fora number of chemical transformation reactions in pharmaceutical industries, such as group protection and deprotection, selective acylation and deacylation, selective hydrolysis, deracemization, kinetic resolution of racemic mixtures, esterification, transesterification, and many others. In this review, an overview of the enzymes, their production and their applications in pharmaceutical syntheses and enzyme therapies are presented with diagrams, reaction schemes and table for easy understanding of the readers.

Genome-Wide Identification and Expression Analysis of the Protease Inhibitor Gene Families in Tomato

The protease inhibitors (PIs) in plants are involved primarily in defense against pathogens and pests and in response to abiotic stresses. However, information about the PI gene families in tomato (Solanumlycopersicum), one of the most important model plant for crop species, is limited. In this study, in silico analysis identified 55 PI genes and their conserved domains, phylogenetic relationships, and chromosome locations were characterized. According to genetic structure and evolutionary relationships, the PI gene families were divided into seven families. Genome-wide microarray transcription analysis indicated that the expression of SlPI genes can be induced by abiotic (heat, drought, and salt) and biotic (Botrytiscinerea and tomato spotted wilt virus (TSWV)) stresses. In addition, expression analysis using RNA-seq in various tissues and developmental stages revealed that some SlPI genes were highly or preferentially expressed, showing tissue- and developmental stage-specific expression profiles. The expressions of four representative SlPI genes in response to abscisic acid (ABA), salicylic acid (SA), ethylene (Eth), gibberellic acid (GA). and methyl viologen (MV) were determined. Our findings indicated that PI genes may mediate the response of tomato plants to environmental stresses to balance hormone signals. The data obtained here will improve the understanding of the potential function of PI gene and lay a foundation for tomato breeding and transgenic resistance to stresses.

Serine protease inhibitors and human wellbeing interplay: new insights for old friends

Serine Protease Inhibitors (Serpins) control tightly regulated physiological processes and their dysfunction is associated to various diseases. Thus, increasing interest is given to these proteins as new therapeutic targets. Several studies provided functional and structural data about human serpins. By comparison, only little knowledge regarding bacterial serpins exists. Through the emergence of metagenomic studies, many bacterial serpins were identified from numerous ecological niches including the human gut microbiota. The origin, distribution and function of these proteins remain to be established. In this report, we shed light on the key role of human and bacterial serpins in health and disease. Moreover, we analyze their function, phylogeny and ecological distribution. This review highlights the potential use of bacterial serpins to set out new therapeutic approaches.

Enzymatic Pea Protein Hydrolysates Are Active Trypsin and Chymotrypsin Inhibitors

In this work, we report the potency of enzymatic hydrolysates of pea proteins against trypsin and chymotrypsin. Pea protein concentrate was digested with each of alcalase, chymotrypsin, pepsin, and trypsin, followed by membrane separation of the protein hydrolysates into peptide fractions (<1, 1-3, 3-5, and 5-10 kDa). Peptide size profiling with size-exclusion gel chromatography indicated the narrowest size range (0.85-4.98 kDa) for alcalase. Trypsin activity was strongly (p < 0.05) inhibited by the ultrafiltration fractions (mean IC50 = 2.2 mg/mL) obtained from the trypsin hydrolysate when compared to the unfractionated hydrolysate (IC50 = 6.8 mg/mL). Similarly, ultrafiltration also enhanced trypsin inhibition by the alcalase-digested peptides with an IC50 of 21.4 mg/mL for the unfractionated hydrolysate in comparison to 3.1-4.7 mg/mL for the fractions. However, ultrafiltration did not enhance trypsin inhibitory activity of chymotrypsin-digested peptides, while the peptide separation reduced efficacy of pepsin-digested peptides. In contrast, chymotrypsin inhibition by all the enzymatic digests was significantly (p < 0.05) enhanced by ultrafiltration, especially peptide sizes >3 kDa. Kinetics of enzyme inhibition indicate peptides were bound to the enzyme active site in a competitive mode that led to reduced catalysis. We conclude that the pea peptides could function as useful tools to promote human health and as a preservative during food processing and storage.

Potential Anticoagulant Activity of Trypsin Inhibitor Purified from an Isolated Marine Bacterium Oceanimonas Sp. BPMS22 and its Kinetics

Protease inhibitors control major biological protease activities to maintain physiological homeostasis. Marine bacteria isolated from oligotrophic conditions could be taxonomically distinct, metabolically unique, and offers a wide variety of biochemicals. In the present investigation, marine sediments were screened for the potential bacteria that can produce trypsin inhibitors. A moderate halotolerant novel marine bacterial strain of Oceanimonas sp. BPMS22 was isolated, identified, and characterized. The effect of various process parameters like salt concentration, temperature, and pH was studied on the growth of the bacteria and production of trypsin inhibitor. Further, the trypsin inhibitor was purified to near homogeneity using anion exchange, size exclusion, and affinity chromatography. The purified trypsin inhibitor was found to competitively inhibit trypsin activity with an inhibition coefficient, K_i, of 3.44 ± 0.13 μM and second-order association rate constant, k_ass, of 1.08 × 10³ M^-1 S^-1. The proteinaceous trypsin inhibitor had a molecular weight of approximately 30 kDa. The purified trypsin inhibitor showed anticoagulant activity on the human blood samples.

Modeling of growth kinetics for an isolated marine bacterium, Oceanimonas sp. BPMS22 during the production of a trypsin inhibitor

Protease inhibitors significantly control physiologically relevant protease activities. Protease inhibitors from marine microbial sources are unique due to their rough living environmental conditions. In the present study, a protein protease inhibitor (PI) was produced from marine Oceanimonas sp. BPMS22. Seven different media were screened for the growth of the bacterium and production of PI. Different carbon and nitrogen sources were screened and optimized for the specific protease inhibitor activity. Three different growth models were checked for the best fit of the bacterial growth. A modified Gompertz model was selected as the best model for the growth of Oceanimonas sp. BPMS22 with the maximum specific growth rate of 0.165 hr^-1 and doubling time of 4.2 hr. The production of PI takes place during the non-growing phase of the bacterial growth. A kinetic model for the production of PI during non-growing phase was used for studying various process parameters. From the model, the maximum trypsin inhibitor formation rate of 0.3802 IU per mg of biomass per hour was observed at 49.91 hr.

A novel serine protease from strawberry (Fragaria ananassa): Purification and biochemical characterization

In this study, a protease enzyme was purified from strawberry by using Sepharose-4B-l-tyrosine-p-amino benzoic acid affinity chromatography. The molecular weight of pure protease was determined 65.8 kDa by SDS-PAGE. The single band observed on the gel showed that the enzyme had a single polypeptide chain and was successfully purified. Purification of the protease by the chromatographic method resulted in a 395.6-fold increase in specific activity (3600 U/mg). Optimum pH and temperature for the enzyme were 6 and 40 °C, respectively. The protease was stable at a wide temperature range of 40 to 70 °C and a pH range of 3.0 to 9.0. Co²⁺ ions stimulated protease activity very strongly. Cu²⁺, Hg²⁺, Cd²⁺ and Mn²⁺ ions significantly inhibited protease activity. While 2-propanol completely inhibited the enzyme, the enzyme maintained its activity better in the presence of ethanol and methanol. The strawberry protease showed the highest specificity towards hemoglobin among all the natural substrates tested. The specificity of the enzyme towards synthetic substrates was also investigated and it was concluded that it has broad substrate specificity. The obtained results indicated that this purified protease was highly-likely a serine protease and its activity was significantly affected by the presence of metal ions.