The presence of defense-related compounds in the pitcher fluid
of Nepenthes suggests that the plant actively generates an environment
which is unsuitable for microbes. Consequently, PR-proteins
are employed as well, including PR-1. In case of NmPR-1, the presence
of a signal peptide, the identification of a related peptide in
the pitcher fluid, as well as its glycosylation strongly indicates that
NmPR-1 is secreted into the digestive fluid. Due to the strong proteolytic
activities in the digestive fluid it is comprehensible that
many plant-derived proteins need to be protected by modifications
such as glycosylation as it has been found for NmPR-1. Its antibacterial,
in place of antifungal, activity however was an unexpected
feature that nicely indicates the importance for a detailed analysis
of obviously known proteins.