Chymotrypsin from the hepatopancreas of cuttlefish (Sepia officinalis) with high activity in the hydrolysis of long chain peptide substrates: Purification and biochemical characterisation

Virtual screening and structure optimization of xanthine oxidase inhibitory peptides from whole protein sequences of Pacific white shrimp via molecular docking

Xanthine oxidase (XO) inhibitory peptides are safer than conventional pharmacological therapy in relieving hyperuricemia. However, traditional enzymatic hydrolysis, separation, and purification techniques for bio-active peptide preparation are time-consuming, inefficient, and labor-intensive. In this study, molecular docking and BLAST were used to virtually screen XO inhibitory peptides from whole protein sequences of Pacific white shrimp according to the bio-active peptides database, and the structure of peptides was optimized based on the structure-effective relationship. Seven new XO inhibitory peptides were virtual screened rapidly from Pacific white shrimp, and YNITGW (IC50 = 9.78 ± 0.13 mM) showed the strongest activity. The results of YNITGW optimization showed that the insertion of Trp residue in the middle position of peptides could effectively enhance the activity. This study revealed that screening and optimizing peptides by molecular docking were a novel and feasible method to obtain bio-active peptides.

Cromatografía de interacción hidrofóbica como método de separación de proteasas alcalinas de vísceras de Scomberomorus sierra

Este estudio se enfocó en recuperar proteasas alcalinas de vísceras de Scomberomorus sierra  mediante cromatografía de interacción hidrofóbica. Tres proteasas alcalinas se lograron separar parcialmente usando esta técnica cromatográfica; dos de ellas con pesos moleculares de 19 y 31 kDa fueron identificadas como enzimas tipo tripsina de acuerdo a ensayos de inhibición. La proteasa alcalina con peso molecular de 31 kDa, única enzima aislada, fue purificada bajo las siguientes condiciones cromatográficas: sulfato de amonio l3% (p/v) y etilenglicol al 27% (p/v); esta enzima mostró actividad máxima a pH 9 – 10 y 50 – 60 °C y fue fuertemente inhibida por el inhibidor de tripsina de soya (SBTI) como por el inhibidor de tripsina porcina (TPI). Una tercera proteasa alcalina con peso molecular de 20 kDa fue parcialmente separada e inhibida por tosil fenilalanil clorometil cetona (TPCK), la cual mostró actividad óptima a pH 9 – 11 y 60 °C. Estos resultados muestran que las vísceras de Scomberomorus sierra podrían ser de utilidad como fuente de proteasas.

Extraction of Cathepsin D-Like Protease from Neon Flying Squid (Ommastrephes bartramii) Viscera and Application in Antioxidant Hydrolysate Production

A protease from neon flying squid (Ommastrephes bartramii) viscera (SVCE3(f)) was partially purified by isoelectric solubilization/precipitation combined with ultra-membrane filtration (ISP-UMF). Two protein bands of 45 and 27 KDa were determined by SDS-PAGE assay. The protease characteristic of the protein band of 45 KDa was confirmed using casein zymography analysis. The result of UPLC-ESI-MS/MS suggested that the band of 45 KDa could be a cathepsin D-like protease. This cathepsin D-like protease showed an optimum pH of 3.0 and optimum temperature of 60 °C when casein was used as s substrate. Furthermore, its protease activity was stable at 30–50 °C and under a pH range of 1.0–5.0, maintaining about 60% of its initial activity. SVCE3(f) can digest half-fin anchovy (Setipinna taty) to generate antioxidant hydrolysates (HAHp-SEs). The degree of hydrolysis (DH) of HAHp-SEs increased along with the hydrolysis time and reached stability after 60 min of digestion. HAHp-SEs(30) with relatively lower DH exhibited the highest DPPH radical scavenging activity as compared with other HAHp-SEs. However, a stronger hydroxyl radical scavenging activity and greater reducing power were observed for HAHp-SEs that underwent higher DH. Accordingly, the partially purified cathepsin D-like protease of neon flying squid viscera using ISP-UMF could have potential application in antioxidant hydrolysates production.

Label-free fluorometric detection of chymotrypsin activity using graphene oxide/nucleic-acid-stabilized silver nanoclusters hybrid materials

Pancreatic function tests are used to determine the presence of chronic pancreatitis, particularly in the early stage of the disease. Chymotrypsin is an indicator of pancreatic function and is thus related to pancreatic diseases. A new fluorescent biosensing method for assay of chymotrypsin activity was developed using DNA (dC₁₂)-templated silver nanoclusters and graphene oxide (GO). A peptide probe was also designed using chymotrypsin-cleavable amino acid sequence and a cysteine terminus. The peptide probe formed Ag-S bond to dC₁₂-AgNCs to enhance the fluorescence of dC₁₂-AgNCs. After the addition of GO, the peptide was adsorbed to the negative GO surface and the fluorescence of dC₁₂-AgNCs was quenched by FRET. The peptide was then degraded into amino acid fragments upon addition of chymotrypsin; these fragments were released from the GO surface, and the FRET was terminated. The developed label-free method features lower cost and higher sensitivity to chymotrypsin activity assay compared with conventional fluorescence analysis. The method can be used to analyze chymotrypsin (as low as 3ng/mL, signal/noise =3) across a dynamic range of 0.0-50.0ng/mL. The proposed biosensing strategy can also be extended to other proteases by using different peptide substrates.

A highly selective marker reaction for measuring the activity of human carboxylesterase 1 in complex biological samples

NMHN hydrolysis was found to be a highly selective marker reaction for sensing the activity of human carboxylesterase 1 (hCE1).

A chymotrypsin from the Digestive Tract of California Spiny Lobster, Panulirus interruptus: Purification and Biochemical Characterization

A chymotrypsin was purified from the gastric juice of California spiny lobster (Panulirus interrutpus), using preparative electrophoresis and affinity chromatography on agarose-p-aminobenzamidine. The molecular mass was estimated by polyacrylamide gel electrophoresis (SDS-PAGE) under denaturing conditions to be 28 kDa. Chymotrypsin activity was totally inhibited by phenylmethylsulfonyl fluoride (PMSF) and chymostatin. Lobster chymotrypsin had optimal pH 7.0-8.0 and temperature of 55 °C. The enzyme is highly stable under a wide range of pH (retaining up to 80 % of activity after 1 h of incubation at pH 3.0, 5.0, and 12.0), showing higher stability at pH 8.0, and was inactivated after 20 min at 55 °C. Lobster chymotrypsin was able to hydrolyze protein substrates at as low as pH 3.0. These results are consistent with the findings of enzyme stability. Activity was assessed after incubation of enzyme with different organic solvents (in the range of 10-50 %); when tested in the presence of acetone, ethanol, propanol, and butanol, lobster chymotrypsin residual activity was >80 %; whereas in the presence of dimethyl sulfoxide (DMSO) and toluene, lobster chymotrypsin residual activity was <80 %. Deduced amino acid sequence, corroborated by mass spectrometry, was determined.

Physiological perturbations in juvenile cuttlefish Sepia officinalis induced by subchronic exposure to dissolved zinc

Although cephalopod early life stage development often occurs in coastal areas where contamination is real and continuous, the physiological perturbations induced by contaminants have been rarely investigated. This study focused on the Zn as it is one of the trace metals the most concentrated in coastal waters, worldwide. As Zn-tolerance limits were unknown in juvenile Sepia officinalis, the aim of this study was to estimate the threshold inducing mortality during the 2-first weeks post-hatching, and to determine its sensitivity using digestive and immune enzymatic assays, as well as growth and behavior follow-up during the first 5weeks post-hatching. Our study highlighted a Zn-mortality threshold lying between 185 and 230μgl(-1), and growth reductions occurring after 5-week at 108μgl(-1) and above, associated with enzymatic perturbations. These results underline a relatively important sensitivity of juvenile cuttlefish to Zn, pointed out by a wide diversity of biomarkers.

Endosymbiotic and host proteases in the digestive tract of the invasive snail Pomacea canaliculata: diversity, origin and characterization

Digestive proteases of the digestive tract of the apple snail Pomacea canaliculata were studied. Luminal protease activity was found in the crop, the style sac and the coiled gut and was significantly higher in the coiled gut. Several protease bands and their apparent molecular weights were identified in both tissue extracts and luminal contents by gel zymography: (1) a 125 kDa protease in salivary gland extracts and in the crop content; (2) a 30 kDa protease throughout all studied luminal contents and in extracts of the midgut gland and of the endosymbionts isolated from this gland; (3) two proteases of 145 and 198 kDa in the coiled gut content. All these proteases were inhibited by aprotinin, a serine-protease inhibitor, and showed maximum activity between 30°C and 35°C and pH between 8.5 and 9.5. Tissue L-alanine-N-aminopeptidase activity was determined in the wall of the crop, the style sac and the coiled gut and was significantly higher in the coiled gut. Our findings show that protein digestion in P. canaliculata is carried out through a battery of diverse proteases originated from the salivary glands and the endosymbionts lodged in the midgut gland and by proteases of uncertain origin that occur in the coiled gut lumen.