Induction of leucine aminopeptidase (LAP) like activity with wounding and methyl jasmonate in pigeonpea (Cajanas cajan) suggests the role of these enzymes in plant defense in leguminosae

Oilseed rape (Brassica napus): the importance of aminopeptidases in germination under normal and heavy metals stress conditions

BACKGROUND

Oilseed rape is one of the most important oilseed crops worldwide, crucial in the food and feed industries. Different environment and climatic conditions can influence its sustainable cultivation and crop yield. Aminopeptidases are crucial enzymes in many physiological processes in all organisms, including humans, so it is important to learn their behavior in food and feed sources. This study presents, for the first time, a detailed discussion on the importance of aminopeptidases, during the oilseed rape germination process, under standard and stress conditions.

RESULTS

During the germination of oilseed rape under standard conditions, a significant increase in aminopeptidases activity toward N-terminal amino acids - phenylalanine (Phe), alanine (Ala), glycine (Gly), leucine (Leu), proline (Pro), methionine (Met) - was observed. The change was substrate specific, with the highest increase being observed for Gly (3.2-fold), followed by Ala (2.9-fold), Pro (2.5-fold), Met (1.5-fold), and Phe (1.3-fold). Generally, N-terminal Phe was preferentially cleaved. Germination under stress conditions, caused by several heavy metal ions (e.g. divalent copper, zinc, cadmium, and lead ions), negatively influenced the plants' growth and quality, but significantly enhanced the expression of genes encoding aminopeptidases (or potentially activated aminopeptidases precursors), which was related to the dramatic increase of their activity.

CONCLUSIONS

The activity/concentration of aminopeptidases in plants is adjusted to the needs at each stage of development and stress factors occurrence. The most significant increase of activity toward N-terminal Gly and Pro proved the key role of aminopeptidases in the defense mechanisms, by supplying the plants with osmoprotectants and organic nitrogen. The results provide new concepts of oilseed rape growth and cultivation under different conditions. © 2021 Society of Chemical Industry.

Cadmium effects on embryo growth of pea seeds during germination: Investigation of the mechanisms of interference of the heavy metal with protein mobilization-related factors

This work aims to give more insight into mechanisms of action of cadmium (Cd) on germinating pea seeds (Pisum sativum L. var. douce province), specifically the different ways by which Cd cations may interfere with the principal factors involved during germination process, notably storage proteins mobilization, amino acids freeing and proteolytic activities. Obtained results revealed that the process of hydrolysis of main storage proteins showed a significant disruption, which resulted in the decrease of the release of free amino acids, thus imposing a lack in nitrogen supply of essential nutrients to growing embryo under Cd stress. This hypothesis was evidenced by Cd-induced changes occurring in main purified protein fractions; Albumins, Legumins and Vicilins, during their breakdown. Besides, at enzymatic level, the activities of main proteases responsible for this hydrolysis were altered. Indeed, assays using synthetic substrates and specific protease inhibitors followed by protease activity measurements demonstrated that Cd inhibited drastically the total azocaseinolytic activity (ACA) and activities of different proteolytic classes: cysteine-, aspartic-, serine- and metallo-endopeptidases (EP), leucine- and proline-aminopeptidases (LAP and PAP, respectively), and glycine-carboxypeptidases (Gly-CP). The data here presented may suggest that the vulnerability of the embryonic axes towards Cd toxicity could be explained as a result of eventual disruption of metabolic pathways that affect mobilization of reserves and availability of nutrients. In vitro studies suggest that Cd cations may act either directly on the catalytic sites of the proteolytic enzymes, which may cause their deactivation, or indirectly via the generation of oxidative stress and overproduction of free radicals that can interact with enzymes, by altering their activity and structure.

The influence of chosen fungicides on the activity of aminopeptidases in winter oilseed rape during pods development

Cultivation of oilseed rape requires application of specific fungicides. Besides their protective role, they can potentially influence the expression and activity of crucial enzymes in the plant. Among the large number of enzymes expressed in plants, aminopeptidases play a key role in all crucial physiological processes during the whole life cycle (e.g. storage protein mobilization and thus supplying plant with needed amino acids, as well as plant aging, protection and defense responses). In the present paper, we evaluate for the first time, the influence of the treatment of winter oilseed rape with commercially available fungicides (Pictor 400 SC, Propulse 250 SE and Symetra 325 SC), on the activity of aminopeptidases expressed in each plant organ (flowers, leaves, stems and pods separately). Fungicides were applied once, at one of the three stages of oilseed rape development (BBCH 59-61, BBCH 63-65 and BBCH 67-69). The aminopeptidase activity was determined using six different amino acid p-nitroanilides as substrates. The results have shown, that in control plants, at the beginning of intensive pods development and seeds production, hydrophobic amino acids with bulky side chains (Phe, Leu) were preferentially hydrolysed. In control plants, the activity was ~3.5 times higher in stems and pods, compared to leaves. The treatment with all pesticides caused significant increase in aminopeptidases hydrolytic activity toward small amino acids Gly, Ala as well as proline, mostly in flowers and leaves. These amino acids are proven to be crucial in the mechanisms of delaying of plant aging, development of better resistance to stress and plant defense. It can be suggested, that studied fungicides enhance such mechanisms, by activating the expression of genes coding for aminopeptidases, which are active in hydrolysis of N-terminal amino acids such as Gly, Ala, Pro from storage peptides and proteins. Depending on fungicide, the major increase of aminopeptidase activity was observed after application at BBCH 67-69 (Pictor 400 SC and Symetra 325 SC) and BBCH 63-65 (Propulse 250 SE) stages of development. Our study revealed, that agrochemical treatment and time of application, influenced the expression and activity of aminopeptidases, even though they were not molecular targets of applied fungicides. Since aminopeptidases are widely distributed throughout all organisms and are crucial in many key physiological processes, it can be expected, that factors influencing their expression and activity in plants, can also influence these enzymes in other organisms, especially humans and other mammals.

Structural and Biophysical Characterization of Cajanus cajan Protease Inhibitor

CONTEXT

A large number of studies have proven that Protease inhibitors (PIs), specifically serine protease inhibitors, show immense divergence in regulation of proteolysis by targeting their specific proteases and hence, they play a key role in healthcare.

OBJECTIVE

We aimed to access in-vitro anticancer potential of PI from Cajanus cajan (CCPI). Also, crystallization of CCPI was targetted alongwith structure determination and its structure-function relationship.

MATERIALS AND METHODS

CCPI was purified from Cajanus cajan seeds by chromatographic techniques. The purity and molecular mass was determined by SDS-PAGE. Anticancer potential of CCPI was determined by MTT assay in normal HEK and cancerous A549 cells. The crystallization screening of CCPI was performed by commercially available screens. CCPI sequence was subject to BLASTp with homologous PIs. Progressive multiple alignment was performed using clustalw2 and was modelled using ab initio protocol of I-TASSER.

RESULTS

The results showed ~14kDa CCPI was purified in homogeneity. Also, CCPI showed low cytotoxic effects of in HEK i.e., 27% as compared with 51% cytotoxicity in A549 cells. CCPI crystallized at 16°C using 15% PEG 6000 in 0.1M potassium phosphate buffer (pH 6.0) in 2-3weeks as rod or needles visualized as clusters under the microscope. The molecular modelling revealed that it contains 3 beta sheets, 3 beta hairpins, 2 β-bulges, 6 strands, 3 helices, 1helix-helix interaction, 41 β-turns and 27 γ-turns.

DISCUSSION AND CONCLUSION

The results indicate that CCPI may help to treat cancer in vivo aswell. Also, this is the first report on preliminary crystallization and structural studies of CCPI.

Bio-prospecting of cuttle fish waste and cow dung for the production of fibrinolytic enzyme from Bacillus cereus IND5 in solid state fermentation

The process parameters governing the production of fibrinolytic enzyme in solid state fermentation employing Bacillus cereus IND5 and using cuttle fish waste and cow dung substrate were optimized. The pH value of the medium, moisture content, sucrose, casein and magnesium sulfate were considered for two-level full factorial design and pH, casein and magnesium sulfate were identified as the important factors for fibrinolytic enzyme production. Central composite design was applied to investigate the interactive effect among variables (pH, casein and magnesium sulfate) and response surface plots were created to find the pinnacle of process response. The optimized levels of factors were pH 7.8, 1.1% casein and 0.1% magnesium sulfate. Enzyme production was increased 2.5-fold after statistical approach. The enzyme was purified up to a specific activity of 364.5 U/g proteins and its molecular weight was 47 kDa. It was stable at pH 8.0 and was highly active at 50 °C. The mixture of cuttle fish waste and cow dung could find great application as solid substrate for the production of fibrinolytic enzyme.

Responses of proteolytic enzymes in embryonic axes of germinating bean seeds under copper stress

The changes in protease activities in embryonic axes during the first days of bean (Phaseolus vulgaris L.) seed germination were investigated in response to copper stress. Synthetic substrates and specific protease inhibitors have been used to define qualitatively and quantitatively different catalytic classes, particularly endoproteases (EP), carboxypeptidases (CP) and aminopeptidases (AP), then identify which ones were affected in the presence of copper. In fact, a failure in storage proteins mobilization and a disorder of nitrogen supply at enzymatic level occurred in Cu. In fact, Cu inhibited azocaseinolytic activity (ACA) and cysteine-, aspartic-, serine-, and metallo-endopeptidases activities (Cys-EP, Asp-EP, Ser-Ep, and Met-EP, respectively). Besides, Cu affected leucine- and proline-aminopeptidases (LAP and PAP, respectively) and glycine-carboxypeptidases (Gly-CP). The proteolytic responses might also be associated with the decrease in defense capacity in the Cu-treated embryos.

Role of the ubiquitin-proteasome pathway and some peptidases during seed germination and copper stress in bean cotyledons

The role of the ubiquitin (Ub)-proteasome pathway and some endo- and aminopeptidases (EPs and APs, respectively) was studied in cotyledons of germinating bean seeds (Phaseolus vulgaris L.). The Ub system appeared to be important both in the early (3 days) and late (9 days) phases of germination. In the presence of copper, an increase in protein carbonylation and a decrease in reduced -SH pool occurred, indicating protein damage. This was associated with an enhancement in accumulation of malondialdehyde, a major product of lipid peroxidation, and an increase in content of hydrogen peroxide (H2O2), showing oxidative stress generation. Moreover, copper induced inactivation of the Ub-proteasome (EC 3.4.25) pathway and inhibition of leucine and proline aminopeptidase activities (EC 3.4.11.1 and EC 3.4.11.5, respectively), thus limiting their role in modulating essential metabolic processes, such as the removal of regulatory and oxidatively-damaged proteins. By contrast, total trypsin and chymotrypsin-like activities (EC 3.4.21.4 and EC 3.4.21.1, respectively) increased after copper exposure, in parallel with a decrease in their inhibitor capacities (i.e. trypsin inhibitor and chymotrypsin inhibitor activity), suggesting that these endoproteases are part of the protective mechanisms against copper stress.

Characterization of a chemostable serine alkaline protease from Periplaneta americana

BACKGROUND

Proteases are important enzymes involved in numerous essential physiological processes and hold a strong potential for industrial applications. The proteolytic activity of insects' gut is endowed by many isoforms with diverse properties and specificities. Thus, insect proteases can act as a tool in industrial processes.

RESULTS

In the present study, purification and properties of a serine alkaline protease from Periplaneta americana and its potential application as an additive in various bio-formulations are reported. The enzyme was purified near to homogeneity by using acetone precipitation and Sephadex G-100 gel filtration chromatography. Enzyme activity was increased up to 4.2 fold after gel filtration chromatography. The purified enzyme appeared as single protein-band with a molecular mass of ~ 27.8 kDa in SDS-PAGE. The optimum pH and temperature for the proteolytic activity for purified protein were found around pH 8.0 and 60°C respectively. Complete inhibition of the purified enzyme by phenylmethylsulfonyl fluoride confirmed that the protease was of serine-type. The purified enzyme revealed high stability and compatibility towards detergents, oxidizing, reducing, and bleaching agents. In addition, enzyme also showed stability towards organic solvents and commercial detergents.

CONCLUSION

Several important properties of a serine protease from P. Americana were revealed. Moreover, insects can serve as excellent and alternative source of industrially important proteases with unique properties, which can be utilized as additives in detergents, stain removers and other bio-formulations. Properties of the P. americana protease accounted in the present investigation can be exploited further in various industrial processes. As an industrial prospective, identification of enzymes with varying essential properties from different insect species might be good approach and bioresource.

Alterations in the Helicoverpa armigera midgut digestive physiology after ingestion of pigeon pea inducible leucine aminopeptidase

Jasmonate inducible plant leucine aminopeptidase (LAP) is proposed to serve as direct defense in the insect midgut. However, exact functions of inducible plant LAPs in the insect midgut remain to be estimated. In the present investigation, we report the direct defensive role of pigeon pea inducible LAP in the midgut of Helicoverpa armigera (Lepidoptera: Noctuidae) and responses of midgut soluble aminopeptidases and serine proteinases upon LAP ingestion. Larval growth and survival was significantly reduced on the diets supplemented with pigeon pea LAP. Aminopeptidase activities in larvae remain unaltered in presence or absence of inducible LAP in the diet. On the contrary, serine proteinase activities were significantly decreased in the larvae reared on pigeon pea LAP containing diet as compared to larvae fed on diet without LAP. Our data suggest that pigeon pea inducible LAP is responsible for the degradation of midgut serine proteinases upon ingestion. Reduction in the aminopeptidase activity with LpNA in the H. armigera larvae was compensated with an induction of aminopeptidase activity with ApNA. Our findings could be helpful to further dissect the roles of plant inducible LAPs in the direct plant defense against herbivory.

Role of the Arabidopsis leucine aminopeptidase 2

Proteolysis-related genes have diverse functions across taxa and have long been considered as key players for intracellular protein turnover. Growing evidence indicates the biological significance of peptidases in degradation, maturation and modulation of bioactive peptides/proteins. By screening T-DNA tagged lines and functional analysis approaches we unraveled the Arabidopsis leucine aminopeptidase (AtLAP2) function in amino acid turnover. Transcriptomics and metabolomics profiling data suggested involvement of AtLAP2 in specific metabolic pathways. Loss-of-function of AtLAP2 resulted in early-leaf senescent and stress-sensitive phenotypes. Our work indicates an important in planta role for AtLAP2 contributing to a further understanding of the proteases having several implications in higher plants.