title: Purification of properoxinectin, a myeloperoxidase homologue and its activation to a cell adhesion molecule.
abstract: Peroxidases are important mediators of innate immune reactions throughout the animal kingdom. In many arthropods a myeloperoxidase homologue, peroxinectin, is known to function as a cell adhesion factor and an opsonin. Here, we report in the freshwater crayfish Pacifastacus leniusculus the isolation of properoxinectin, inactive in cell adhesion, and we also show that properoxinectin is produced in the mature blood cells whereas the hematopoietic tissue contains very little of this protein. Both properoxinectin and peroxinectin are catalytically active as peroxidases, at least when using low molecular weight substrates. The extracellular processing of properoxinectin into an active cell adhesion protein was found to involve proteolytic steps shared with the prophenoloxidase activating system to yield catalytically active phenoloxidase. Thus, the regulation of activities by two ancient metalloproteins, both potentially producing highly toxic substances aimed at pathogens, is carried out by limited proteolysis. The proteolytic processing is triggered in the presence of microbial compounds such as beta-glucans or lipopolysaccharide after the release of properoxinectin and prophenoloxidase activating serine proteinases from the blood cells.
authors.affiliation: Department of Comparative Physiology, Uppsala University, Norbyvägen 18A, SE-752 36 Uppsala, Sweden.
authors.forename: Xionghui
authors.initials: X
authors.lastname: Lin
authors.forename: Lage
authors.initials: L
authors.lastname: Cerenius
authors.forename: Bok Luel
authors.initials: BL
authors.lastname: Lee
authors.forename: Kenneth
authors.initials: K
authors.lastname: Söderhäll
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003400:Astacoidea; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009195:Peroxidase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D015815:Cell Adhesion Molecules; D009195:Peroxidase