Classification, expression systems, structure, functions, and applications of proteases.

Proteases, with their extensive sources and remarkable characteristics such as high catalytic efficiency, substrate specificity, and species diversity, have long attracted widespread attention and are widely applied in various fields including food processing, detergent production, pharmaceutical, and environmental protection; these enzymes can hydrolyze proteins into peptides and amino acids, thereby participating in crucial physiological activities like digestion and immune regulation, and playing an indispensable role in maintaining the health and daily life of organisms. Moreover, through artificial synthesis of the required proteases, it is possible to achieve efficient large-scale expression and production, which significantly reduces industrial costs, making them more economically viable in practical applications. This paper provides a comprehensive review of proteases, covering their classification, sources, structure-activity relationships, and industrial applications, and constructs a closed-loop analytical framework based on "basic characteristics, production technology, and practical application" to systematically organize and analyze the relevant information; in particular, it quantitatively compares the advantages and defects of expression systems using Escherichia coli, yeast, and Bacillus subtilis, which not only deepens the understanding of these systems but also provides valuable theoretical support for the rational selection of expression vectors in different scenarios, and introduces their development prospects in food, medicine, environmental protection, and related fields. The insights provided herein offer specific directions for future applied research on artificially engineered proteases. [ABSTRACT FROM AUTHOR]