LYZL6 (lysozyme-like 6) is a c-type lysozyme homolog with dual functions in male reproductive physiology and innate immunity. Primary Function: LYZL6 is selectively expressed in the testis and epididymis 1 and localizes to the post-acrosomal membrane and midpiece of mature spermatozoa 21. The protein plays a critical role in sperm-egg fusion, with immunoneutralization studies demonstrating dose-dependent inhibition of human sperm-hamster egg fusion in vitro 1. Mechanism: LYZL6 exhibits bacteriolytic activity against Gram-positive bacteria (Micrococcus lysodeikticus and Staphylococcus aureus) with pH-dependent activity peaking at pH 5.6 13. However, its bacteriolytic activity is substantially weaker than human lysozyme under physiological conditions 1. The protein may function as a hydrolase in zona pellucida penetration during fertilization 3. Disease Relevance: LYZL6 has emerged as a cancer-testis (CT) gene biomarker, aberrantly expressed in 15% of colon cancer tissues 4 and reactivatable through epigenetic drugs in cancer cells 5. Clinical Significance: The distinctive expression pattern and dual functionality position LYZL6 as a potential target for both cancer diagnostics and antimicrobial therapeutics.