Lysozyme plays an important role in human innate immunity by causing bacterial cell lysis. We describe for the first time, the actual performance of human lysozyme g-like 2 (HLysG2), a mammalian g-type lysozyme. RT-PCR revealed that the HLysG2 gene was transcribed in eye and testis tissues. A spot was detected from human tears using 2D gel electrophoresis and was identified as HLysG2 using MALDI-TOF/TOF MS and a MASCOT search with a matching score of 140 and 27% sequence coverage of the whole amino acid sequence. To gain insight into the in vitro antimicrobial activities of HLysG2, the mature peptide-coding region was cloned into Pichia pastoris for heterogeneous expression. Recombinant HLysG2, had an optimal at pH 6.0 and 30 °C, reached the peak activity of 1.2 × 10(4)U/mg at the sodium ion concentration of 75 mM and showed a higher salt tolerance than human c-type lysozyme (HLysC). Recombinant HlysG2 inhibited Gram-positive bacterial growth and did not inhibit Gram-negative bacterial and Candida albicans growth. Results indicated that HLysG2 is a potent antibacterial protein that may play a role in the innate immunity of the human eye.
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