Hemocyanin-derived phenoloxidase reaction products display anti-infective properties

Hemocyanin is a multi-functional protein located in the hemolymph (blood) of certain arthropods and molluscs. In addition to its well-defined role in oxygen transport, hemocyanin can be converted into a phenoloxidase-like enzyme. Herein, we tested the antimicrobial properties of horseshoe crab (Limulus polyphemus) hemocyanin-derived phenoloxidase reaction products using broad ranges of phenolic substrates (e.g. L-DOPA) and microbial targets (Gram-positive/negative bacteria, yeast). The enzyme-catalysed turnover of several substrates generated (by)products that reduced significantly the number of colony forming units. Microbicidal effects of hemocyanin-derived phenoloxidase were thwarted by the inhibitor phenylthiourea. Data presentedhere further support a role for hemocyanin in invertebrate innate immunity

Antiviral activity of hemocyanins

Hemocyanins are giant biological macromolecules acting as oxygen-transporting glycoproteins. Most of them are respiratory proteins of arthropods and mollusks, but besides they also exhibit protecting effects against bacterial, fungal and viral invasions. As discovered by 2-DGE proteomics analyses, several proteins including hemocyanins of hemocytes from virus-infected arthropods increased upon infection, confirming hemocyanin’s role as part of the organism’s defence system. Based on the structural analyses of molluscan Hcs it is suggested that the carbohydrate chains of the glycoproteins seem to interact with surface-exposed amino acid or carbohydrate residues of the viruses through van der Waals interactions