Systematic mining and engineering of signal peptides to achieve efficient secretion of cephalosporin C acylase in Escherichia coli

Cephalosporin C acylases (CCAs) catalyze the hydrolysis of cephalosporin C to 7-aminocephalosporanic acid, a key intermediate for semisynthetic cephalosporin antibiotics. The functional secretion of heterologous CCAs in Escherichia coli is often constrained by signal peptide efficiency. To enhance the production of the engineered CCA mutant A14 from Bosea sp. OK403, we performed systematic signal peptide screening and identified the native SP AsPGA as most effective. Following codon optimization to generate SP AsPGA∗ , targeted mutagenesis of its N-, H-, and C-regions produced the superior H9 mutant (C16A). This variant increased extracellular A14 expression and activity by 6.26-fold and 2.0-fold, respectively. Molecular dynamics simulations indicated the C16A substitution stabilizes the signal peptide conformation and facilitates SecA translocon interaction. This work establishes that systematic mining and engineering of signal peptides, particularly through mutations that enhance structural stability, is a powerful strategy for optimizing the secretory production of complex enzymes in recombinant systems. Strategy to enhance CPC acylase secretion in Escherichia coli via signal peptide mining, screening, and optimization, followed by structural analysis and molecular dynamics simulations of the resulting mutants.