The Hydrolase, Glycosidase, Antimicrobial, and Bacteriolytic enzyme keywords are the source of the catalytic activity, hydrolase activity, hydrolase activity acting on glycosyl bonds, defense response to bacterium, and killing of cells of another organism annotations.

The Gram-positive and Gram-negative defence terms were propagated from the PANTHER lysozyme C tree. The same propagation gives the human orthologue its GO:0050829 annotation, and the human GO:0050830 annotation is additionally supported by direct assay.

Lysozyme activity was assigned from the UniProtKB EC number 3.2.1.17.

Mammalian c-type lysozymes are innate immune effectors that kill bacteria by degrading the peptidoglycan of their cell walls. This is the general statement of function against which the vampire bat gene was analysed.

The common vampire bat, like the other phyllostomid bats analysed, has a single c-type lysozyme gene - in contrast to the insectivorous bat clade in which lysozyme was duplicated and adapted for chitin digestion. This constrains functional interpretation of K9IWH5: there is no paralogue to which a digestive role could be partitioned.

Positive selection was detected on the mature lysozyme along the lineages leading to vampire bats but not in other single-copy bats, and several sanguivore-specific substitutions are predicted to have functional impacts.

The authors interpret this adaptation as antimicrobial rather than digestive, driven by the specialised sanguivorous habits of vampire bats.

Lysozyme is one of the antimicrobials that dominate the accessory submaxillary gland of D. rotundus, expressed there at higher levels than in the principal gland and confirmed by both transcriptome and proteome analysis. This is the study behind the salivary gland EMBL record (JAA45151.1) in the UniProt entry.

Lysozyme was also among the proteins directly identified by LC-MS/MS in the gland proteome, establishing that the protein - not only the transcript - is present in the secretory tissue.

The gene is named LYZ, the protein carries EC 3.2.1.17 with the explicit muramidase reaction, and it belongs to glycosyl hydrolase family 22 (PANTHER subfamily PTHR11407:SF28 LYSOZYME C).

A SignalP-predicted signal peptide (1-18) is cleaved to give the mature 19-148 chain, consistent with a secreted protein.

Three independent transcript sources underlie the entry: two vampire bat submaxillary/salivary gland transcriptomes and one liver transcript from the adaptive evolution study.

The Gram-positive preference of GH22 lysozymes is a matter of substrate accessibility rather than catalytic specificity; the outer membrane of Gram-negative bacteria must be compromised for robust activity.

The report notes that its functional assignment is a GH22 family inference and supports extracellular localisation as the primary functional context.