The o-diphenol oxidase activity of arthropod hemocyanin.
Arthropod hemocyanin (isolated from the crab Carcinus maenas and the lobster Homarus americanus) is usually referred to as an oxygen transport-storage protein. The protein, however, also catalyses with low efficiency the oxidation of o-diphenol to quinone, similarly to tyrosinase (monophenol, o-diphenol:oxygen oxidoreductase). The enzymatic parameters of hemocyanin are affected by the aggregation state of the protein; namely V(max) exhibited by a dissociated subunit is one order of magnitude greater than that of aggregated species. The reaction velocity is increased by the presence of perchlorate, an anion of the Hofmeister series. The results are also discussed on the basis of active site accessibility in comparison with tyrosinase.
Zlateva
T
T
Department of Biology, University of Padova, Italy.
Di Muro
P
P
Salvato
B
B
Beltramini
M
M
D000818:Animals; D003386:Brachyura / Q000737:chemistry*; D004156:Catechol Oxidase / Q000378:metabolism*; D002396:Catechols / Q000378:metabolism; D006433:Hemocyanins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D008121:Nephropidae / Q000737:chemistry*; D010084:Oxidation-Reduction; D010472:Perchlorates / Q000737:chemistry / Q000494:pharmacology; D011487:Protein Conformation; D011809:Quinones / Q000378:metabolism; D017670:Sodium Compounds / Q000737:chemistry / Q000494:pharmacology; D013997:Time Factors
D002396:Catechols; D010472:Perchlorates; D011809:Quinones; D017670:Sodium Compounds; D006433:Hemocyanins; C031068:sodium perchlorate; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase; C034221:catechol