Cloning, Expression, and Characterization of GDSL-Type Lipolytic Enzyme Genes from Epidermidibacterium keratini EPI-7 Isolated from Human Skin.

This study investigated seven putative lipolytic enzymes (EstEk01-07) from the skin microbiome bacterium Epidermidibacterium keratini EPI-7, focusing on their properties relevant to industrial applications. Sequence analysis revealed conserved GDSL motifs and four conserved blocks, characteristic of the GDSL/SGNH superfamily, with predicted α/β/α folds consistent with these enzymes. Significant variations in the number of α-helices and β-sheets among the EstEk enzymes suggested diverse substrate specificities and catalytic efficiencies. The enzymes exhibited a strong preference for short-chain fatty acids (C2-C4), classifying them as carboxylesterases, a novel finding within the skin microbiome. Optimal enzyme activity was observed at alkaline pH (8.0-9.0) and thermophilic condition (50-60°C), with substantial thermostability retained after heating at 50°C for three hours. Metal ion analysis revealed a significant stimulatory effect of Ca²⁺ and Fe³⁺, while other transition metals were inhibitory. The enzymes were stable in a range of non-ionic detergents, but sensitive to SDS. Moreover, they exhibited notable tolerance to various organic solvents, particularly methanol and isopropanol, suggesting potential applications in cosmetics and pharmaceutical industries. This study identifies a novel library of thermostable, alkaline carboxylesterases from the skin microbiome, highlighting their potential for industrial biocatalysis and further investigation into their role in skin lipid metabolism.