Effects of heat treatment and germination on trypsin and chymotrypsin inhibitory activities in sorghum (Sorghum bicolor (L.) Moench) seeds

Physicochemical Properties and Elimination of the Activity of Anti-Nutritional Serine Protease Inhibitors from Mulberry Leaves

Mulberry leaf is an excellent protein resource that can be used as feed additive for livestock and poultry. Nevertheless, the use of mulberry leaves in animal diets is limited by its protease inhibitors, tannic acid and other anti-nutritional factors. This study systematically analyzed the type and activity of serine protease inhibitors (SPIs) from the leaves of 34 mulberry varieties, aiming to reveal the physicochemical properties and inactivation mechanism of SPIs. The types and activities of trypsin inhibitors (TIs) and chymotrypsin inhibitors (CIs) exhibited polymorphisms among different mulberry varieties. The highest number of types of inhibitors was detected in Jinshi, with six TIs (TI-1~TI-6) and six CIs (CI-1~CI-6). TIs and CIs exhibited strong thermal and acid–base stability. High-temperature and high-pressure treatment could reduce the activities of TIs and CIs to a certain extent. β-mercaptoethanol treatment could completely abolish TIs and CIs, suggesting that the disulfide bridges were critical for their inhibitory activities. The Maillard reaction could effectively eliminate the inhibitory activities of TI-1~TI-4 and CI-1~CI-4. This study reveals the physicochemical properties and inactivation mechanisms of the anti-nutritional SPIs from mulberry leaves, which is helpful to exploit mulberry-leaf food with low-activity SPIs, promote the development and utilization of mulberry-leaf resources in animal feed and provide reference for mulberry breeding with different functions.

Coix lacryma-jobi chymotrypsin inhibitor displays antifungal activity

A novel chymotrypsin inhibitor, named ClCI, was purified from coix seed (Coix lacryma-jobi L.) by aqueous two-phase extraction, chymotrypsin-Sepharose 4B affinity chromatography and centrifugal ultrafiltration. ClCI was a 7.9 kDa competitive inhibitor with pI 6.54. The inhibition constants (K_i) for bovine pancreatic chymotrypsin and bacterial subtilisin were 1.27 × 10^-10 M and 1.57 × 10^-9 M respectively. ClCI had no inhibitory activity against bovine trypsin and porcine elastase. ClCI had wide pH stability and good heat resistance. It can maintain >90% inhibition activity against chymotrypsin at 20-80 °C for 1 h. The primary structure of ClCI was highly similar (57%-92%) to those of several inhibitors belonging to the Gramineae crop potato protease inhibitor- I superfamily and showed the typical sequence motif of the protease inhibitor of the seed storage protein group. ClCI (12.5 mg) inhibited mycelial growth of the phytopathogenic fungi Mycosphaerella melonis, Helminthosporium turcicum, Alternaria solani, Phytophthora capsici, Isariopsis griseola, and Colletotrichum gloeosporioides, and caused 89% inhibition of the proteases from spore germination of plant-pathogenic fungi. The results of the present study indicate that ClCI had biotechnological potential as an alternative agent to combat the important phytopathogenic fungi.