TY - JOUR
T1 - Characterization of phenoloxidase activity in Sydney rock oysters (Saccostrea glomerata)
AU - Aladaileh, Saleem
AU - Peters, Rodney
AU - Nair, Sham V.
AU - Raftos, David A.
PY - 2007/12
Y1 - 2007/12
N2 - Phenoloxidase (PO) activity was studied in Sydney rock oysters (Saccostrea glomerata). As in other molluscs, PO was found to exist as a pro-enzyme (proPO) in hemocytes. ProPO could be activated to PO by exogenous proteases (trypsin and chymotrypsin), exposure of hemocytes to pathogen-associated molecular patterns (PAMPs) and by the detergents, Triton X-100 and sodium dodecyl sulphate (SDS). Inhibition studies confirmed the proPO activating system of Sydney rock oysters is a proteinase cascade in which Ca2+ dependent serine proteinases proteolytically convert proPO into active PO. Activated PO was found to be a tyrosinase-like enzyme that is responsible for both monophenolase and diphenolase activity. The bifunctional PO had higher affinity for the monophenol, hydroquinine monomethyl ether (4HA) (Km = 4.45 ± 1.46 mM) than for the diphenol, l-DOPA (Km = 10.27 ± 1.33 mM). Maximum enzyme activity was evident at 37 °C, pH 8 and at salinities of between 30 and 37 ppt. Melanogenesis catalysed by the active enzyme is a composite of eumelanin and the product of a sclerotin pathway combining DOPA decarboxylase with PO activity.
AB - Phenoloxidase (PO) activity was studied in Sydney rock oysters (Saccostrea glomerata). As in other molluscs, PO was found to exist as a pro-enzyme (proPO) in hemocytes. ProPO could be activated to PO by exogenous proteases (trypsin and chymotrypsin), exposure of hemocytes to pathogen-associated molecular patterns (PAMPs) and by the detergents, Triton X-100 and sodium dodecyl sulphate (SDS). Inhibition studies confirmed the proPO activating system of Sydney rock oysters is a proteinase cascade in which Ca2+ dependent serine proteinases proteolytically convert proPO into active PO. Activated PO was found to be a tyrosinase-like enzyme that is responsible for both monophenolase and diphenolase activity. The bifunctional PO had higher affinity for the monophenol, hydroquinine monomethyl ether (4HA) (Km = 4.45 ± 1.46 mM) than for the diphenol, l-DOPA (Km = 10.27 ± 1.33 mM). Maximum enzyme activity was evident at 37 °C, pH 8 and at salinities of between 30 and 37 ppt. Melanogenesis catalysed by the active enzyme is a composite of eumelanin and the product of a sclerotin pathway combining DOPA decarboxylase with PO activity.
UR - http://www.scopus.com/inward/record.url?scp=35648965656&partnerID=8YFLogxK
U2 - 10.1016/j.cbpb.2007.07.089
DO - 10.1016/j.cbpb.2007.07.089
M3 - Article
VL - 148
SP - 470
EP - 480
JO - Comparative Biochemistry and Physiology - Part B: Biochemistry and Molecular Biology
JF - Comparative Biochemistry and Physiology - Part B: Biochemistry and Molecular Biology
SN - 1096-4959
IS - 4
ER -