Evaluation of cardosin A as a probe for limited proteolysis in non-aqueous environments—complex substrates hydrolysis

Production of hydrophobic amino acids from biobased resources: wheat gluten and rubber seed proteins

Protein hydrolysis enables production of peptides and free amino acids that are suitable for usage in food and feed or can be used as precursors for bulk chemicals. Several essential amino acids for food and feed have hydrophobic side chains; this property may also be exploited for subsequent separation. Here, we present methods for selective production of hydrophobic amino acids from proteins. Selectivity can be achieved by selection of starting material, selection of hydrolysis conditions, and separation of achieved hydrolysate. Several protease combinations were applied for hydrolysis of rubber seed protein concentrate, wheat gluten, and bovine serum albumin (BSA). High degree of hydrolysis (>50 %) could be achieved. Hydrophobic selectivity was influenced by the combination of proteases and by the extent of hydrolysis. Combination of Pronase and Peptidase R showed the highest selectivity towards hydrophobic amino acids, roughly doubling the content of hydrophobic amino acids in the products compared to the original substrates. Hydrophobic selectivity of 0.6 mol-hydrophobic/mol-total free amino acids was observed after 6 h hydrolysis of wheat gluten and 24 h hydrolysis of rubber seed proteins and BSA. The results of experiments with rubber seed proteins and wheat gluten suggest that this process can be applied to agro-industrial residues.

Multiplicity of aspartic proteinases from Cynara cardunculus L

Aspartic proteinases (AP) play major roles in physiologic and pathologic scenarios in a wide range of organisms from vertebrates to plants or viruses. The present work deals with the purification and characterisation of four new APs from the cardoon Cynara cardunculus L., bringing the number of APs that have been isolated, purified and biochemically characterised from this organism to nine. This is, to our knowledge, one of the highest number of APs purified from a single organism, consistent with a specific and important biological function of these protein within C. cardunculus. These enzymes, cardosins E, F, G and H, are dimeric, glycosylated, pepstatin-sensitive APs, active at acidic pH, with a maximum activity around pH 4.3. Their primary structures were partially determined by N- and C-terminal sequence analysis, peptide mass fingerprint analysis on a MALDI-TOF/TOF instrument and by LC-MS/MS analysis on a Q-TRAP instrument. All four enzymes are present on C. cardunculus L. pistils, along with cyprosins and cardosins A and B. Their micro-heterogeneity was detected by 2D-electrophoresis and mass spectrometry. The enzymes resemble cardosin A more than they resemble cardosin B or cyprosin, with cardosin E and cardosin G being more active than cardosin A, towards the synthetic peptide KPAEFF(NO(2))AL. The specificity of these enzymes was investigated and it is shown that cardosin E, although closely related to cardosin A, exhibits different specificity.

Cardosins: A new and efficient plant enzymatic tool to dissociate neuronal cells for the establishment of cell cultures

In the present work, we examined the feasibility of using cardosins, plant aspartic-proteinases from Cynara cardunculus L., to isolate cells from rat embryonic brain. Using morphological and functional assays, we compared cell cultures obtained with cardosins with those prepared with a well-established trypsin protocol. Cardosins and trypsin dissociation produced cells with similar yield, viability, and GABA release in response to a depolarizing stimulus. However, cardosins-dissociated cells appeared to recover faster in culture, as assessed by the MTT-test and by the number and length of neurtites, suggesting that cardosins are less aggressive to neurons than trypsin. This feature might be helpful for research and medical purposes requiring fast manipulations of cells.

Effect of acetonitrile on Cynara cardunculus L. cardosin A stability

The kinetics of the structural changes affecting cardosin A, a plant aspartic proteinase (AP) from Cynara cardunculus L., in the presence of a mixture of acetonitrile (AN) in water (W) was studied. Incubation of cardosin A with 10% (v/v) AN resulted in a gradual increase in protein helicity, accompanied by changes in the tertiary structure, seen by changes in the intrinsic fluorescence of tryptophan. Differential scanning calorimetry (DSC) revealed that the temperature of denaturation of cardosin A decreased upon the addition of AN. With longer incubation times, the small chain of cardosin A denatured completely, consequent exposure of the single tryptophan residue accounting well for the observed spectral shift intrinsic fluorescence of the protein. Enzymatic activity assays demonstrated that the kinetically determined unfolding of the small chain of cardosin A does not result in loss of the activity of this enzyme.