Spectroscopic investigations on fungal aspartic protease as target of gallic acid

Proteases are a major virulence factor in pathogenic fungi and can serve as a potential therapeutic target. The interaction of gallic acid (GA) with Aspartic fungal protease (PepA) was investigated using biophysical and in silico approaches. UV-Vis and fluorescence spectroscopy showed complex formation and static quenching of PepA by GA with K_a of 7.4 × 10⁵ M^-1 and stoichiometric binding site (n) of 1.67. CD-spectroscopy showed marked changes in helical content and synchronous fluorescence spectra measurements indicated significant changes in the microenvironment around tryptophan residues in the GA-PepA complex. Outcomes of Isothermal Titration Calorimetry (ITC) measurement and molecular modelling studies validated the spectroscopic results. The binding of GA to Human Serum albumin (HSA) was moderate (K_a = 1.9 × 10³ M^-1) and did not cause structural disruption of HSA. To conclude, gallic acid is strongly bound to fungal protease leading to structural disruption and inhibition whereas HSA structure was largely conserved. Gallic acid thus appears to be a potential therapeutic agent against fungal proteases.

Production of mycelial biomass, proteases and protease inhibitors by Ganoderma lucidum under different submerged fermentation conditions

Ganoderma lucidum is a medicinal mushroom widely recognized as a source of biomolecules with pharmacological properties, however, little is known about the factors that influence the synthesis of bioactive proteins by this fungus when cultivated under submerged fermentation. The objective of this work was to evaluate the production of mycelial biomass and intracellular proteases and protease inhibitors by G. lucidum cultivated under different submerged fermentation conditions. The cultivation was carried out in a medium composed of glucose (10 or 20 g.L-1), soy peptone (2.5 or 5 g.L-1) and yeast extract (5 g.L-1), with incubation under agitation (120 rpm) and non-agitation, totaling 8 experimental conditions. Biomass production was determined from the dry weight, while glucose consumption was estimated by quantification of reducing sugars. The proteins were extracted in NaCl (0.15 M), and the protein extracts were submitted to protein quantification by the Bradford method, total proteolytic activity using azocasein, caseinolytic and fibrinolytic activity in Petri dishes, activity of serine (trypsin and chymotrypsin) and cysteine (papain) protease inhibitors. Cultivation in agitated condition showed higher biomass production with a maximum value of 7 g.L-1, in addition to higher activities of trypsin, chymotrypsin and papain inhibitors, with 154 IU.mg-1, 153 IU.mg-1 e 343 IU.mg-1 of protein, respectively. The non-agitated condition showed a greater potential for obtaining proteins, total proteases, caseinolytic and fibrinolytic enzymes, with maximum values of 433 mg.g-1 of extract, 71 U.mL-1 of extract, 63.62 mm2 and 50.27 mm2, respectively. Thus, a medium composed of soy peptone, yest extract and glucose in a 1:2:4 proportion is recommended, under agitation to produce protease inhibitors, and the non-agitated condition when the target is, mainly caseinolytic and fibrinolytic enzymes.

Some properties and possible biological role of peptidase inhibitors from the entomopathogenic fungus Tolypocladium cylindrosporum

The activities of secreted and mycelial inhibitors of proteolytic enzymes from fungi of the order Hypocreales have been investigated. Inhibitors of bromelain, papain, and trypsin of low molecular mass (about 1 kDa) and a subtilisin proteinaceous inhibitor with molecular mass of 45 kDa were revealed in the culture liquid of the fungus Tolypocladium cylindrosporum. The subtilisin inhibitor from T. cylindrosporum has antibiotic properties, significantly decreased the activity of purified bacterial enzymes, and prevented the growth of the bacterium Pseudomonas sp. Data suggesting the existence in fungi of the Hypocreales order of two pools of peptidase inhibitors have been obtained.

Fungal inhibitors of proteolytic enzymes: classification, properties, possible biological roles, and perspectives for practical use

Peptidase inhibitors are ubiquitous regulatory proteins controlling catalytic activity of proteolytic enzymes. Interest in these proteins increased substantially after it became clear that they can be used for therapy of various important diseases including cancer, malaria, and autoimmune and neurodegenerative diseases. In this review we summarize available data on peptidase inhibitors from fungi, emphasizing their properties, biological role, and possible practical applications of these proteins in the future. A number of fungal peptidase inhibitors with unique structure and specificity of action have no sequence homology with other classes of peptidase inhibitors, thus representing new and specific candidates for therapeutic use. The main classifications of inhibitors in current use are considered. Available data on structure, mechanisms and conditions of action, and diversity of functions of peptidase inhibitors of fungi are analyzed. It is mentioned that on one side the unique properties of some inhibitors can be used for selective inhibition of peptidases responsible for initiation and development of pathogenic processes. On the other side, general inhibitory activity of other inhibitors towards peptidases of various catalytic classes might be able to provide efficient defense of transgenic plants against insect pests by overcoming compensatory synthesis of new peptidases by these pests in response to introduction of a fungal inhibitor. Together, the data analyzed in this review reveal that fungal inhibitors extend the spectrum of known peptidase inhibitors potentially suitable for use in medicine and agriculture.

Inhibition of xyloglucanase from an alkalothermophilic Thermomonospora sp. by a peptidic aspartic protease inhibitor from Penicillium sp. VM24

A bifunctional inhibitor from Penicillium sp VM24 causing inactivation of xyloglucanase from Thermomonospora sp and an aspartic protease from Aspergillus saitoi was identified. Steady state kinetics studies of xyloglucanase and the inhibitor revealed an irreversible, non-competitive, two-step inhibition mechanism with IC(50) and K(i) values of 780 and 500nM respectively. The interaction of o-phthalaldehyde (OPTA)-labeled xyloglucanase with the inhibitor revealed that the inhibitor binds to the active site of the enzyme. Far- and near-UV spectrophotometric analysis suggests that the conformational changes induced in xyloglucanase by the inhibitor may be due to irreversible denaturation of enzyme. The bifunctional inhibitor may have potential as a biocontrol agent for the protection of plants against phytopathogenic fungi.