Two closely related copper proteins, phenoloxidase and haemocyanin, are known to be involved in different physiological functions such as the primary immune response and oxygen transport. Although the proteins differ structurally, they have the same active site by which dioxygen is bound. Recent results reveal that haemocyanin also exhibits phenoloxidase activity. A scenario is proposed for the...

/V-/j-Alanyldopamine (NBAD) has attracted a great deal of interest because of its significance in catecholamine metabolism in insects with which phenoloxidase is concerned.1' Kramer et al. synthesized NBADby coupling the acid component of /V-/?-alanine with the amine component of dopamine in aqueous solution.2' Their method, however, required several chromatographic steps to purify the syntheti...

The enzymatic activity of phenoloxidase is assayed routinely in the presence of SDS. Similar assay conditions elicit phenoloxidase activity in another type 3 copper protein, namely hemocyanin, which normally functions as an oxygen carrier. The nature of the conformational changes induced in type 3 copper proteins by the denaturant SDS is unknown. This comparative study demonstrates that arthrop...

Phenoloxidase activity in crayfish haemocyte lysates and extracts of haemocyte membranes were studied using native PAGE and SDS-PAGE gels and staining for cresolase, catecholase and laccase activities. The activation of the proenzyme, prophenoloxidase to phenoloxidase, in native PAGE was demonstrated following exposure to SDS. By staining samples separated in SDS-PAGE followed by renaturation, ...

Eggs of the parasitoid Leptopilina boulardi, strain L104, are routinely encapsulated by haemocytes in C’rosophila melanogaster larvae, and the capsules subsequently melanize. In D. melanogaster mutant strains deficient for phenoloxidase activity, L104 eggs are encapsulated by host haemocytes but the cellular capsules do not melanize and harden. These observations suggest that phenoloxidases are...

The fungal metabolite kojic acid, which is produced by Aspergillus and Penicillium species fungi that may be pathogens of both insects and plants, was a significant inhibitor of phenoloxidase of different representative beetle and caterpillar insect species. Fusaric acid and picolinic acid, produced by Fusarium spp., were also significant inhibitors of phenoloxidase, while dipicolinic acid and ...

Peroxidase isozymes from winter wheat (Triticum aestivum L. cv Orso) seedlings extracts showed phenoloxidase-like activity, becoming visible on polyacrylamide gels also in the absence of hydrogen peroxide. The results obtained after a characterization of the two activities, based on their substrate specificity, on their selective inhibition, and on the possible occurrence of artifacts, suggeste...