Characterization of a Novel Milk-Clotting Aspartic Protease from Penicillium sp. and Structural Explanation for its High Milk-Clotting Index

A novel milk-clotting enzyme isolated from Penicillium sp. ACCC 39790 (PsMCE) was prepared by heterologous expression. The recombinant PsMCE had an apparent molecular mass of 45 kDa and exhibited maximum casein hydrolysis activity at pH 4.0 and 50 °C. The PsMCE activity was enhanced by calcium ions and strongly inhibited by pepstatin A. Through hydrolysis pattern and cleavage site analyses, the milk-clotting activity of PsMCE was related to its specific hydrolysis between Phe105 and Met106 in the κ-casein proteins. The structural basis of PsMCE was characterized using homology modeling, molecular docking, and interactional analysis. The P1' region of PsMCE is critical for its selective binding to the hydrolytic site in κ-casein, and the hydrophobic forces play a decisive role in the specific cleavage of Phe105 and Met106. These interactional analyses between PsMCE and the ligand peptide clarified the fundamentals of its high milk-clotting index (MCI). PsMCE could be applied in cheese making due to its thermolability and high MCI value as a potential milk-clotting enzyme.

 

Comments:

The passage describes a novel milk-clotting enzyme isolated from Penicillium sp. ACCC 39790 called PsMCE. The enzyme was prepared by heterologous expression and has an apparent molecular mass of 45 kDa. PsMCE exhibits maximum casein hydrolysis activity at pH 4.0 and 50 °C and is enhanced by calcium ions, while strongly inhibited by pepstatin A.

The milk-clotting activity of PsMCE is related to its specific hydrolysis between Phe105 and Met106 in the κ-casein proteins. The structural basis of PsMCE was characterized using homology modeling, molecular docking, and interactional analysis. The P1' region of PsMCE is critical for its selective binding to the hydrolytic site in κ-casein, and the hydrophobic forces play a decisive role in the specific cleavage of Phe105 and Met106.

These interactional analyses between PsMCE and the ligand peptide clarified the fundamentals of its high milk-clotting index (MCI). PsMCE could be applied in cheese making due to its thermolability and high MCI value as a potential milk-clotting enzyme.

In summary, PsMCE is a promising milk-clotting enzyme that has potential applications in the cheese-making industry. Its specific hydrolysis activity on κ-casein proteins and the understanding of its structural basis will allow for the development of more efficient and effective milk-clotting enzymes in the future.

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