TAILIEUCHUNG - Báo cáo khoa học: Kinetic properties of catecholoxidase activity of tarantula hemocyanin

Phenoloxidases occur in almost all organisms, being essentially involved in various processes such as the immune response, wound healing, pigmenta-tion and sclerotization in arthropods. Many hemocyanins are also capable of phenoloxidase activity after activation. | ễFEBS Journal Kinetic properties of catecholoxidase activity of tarantula hemocyanin Elmar Jaenicke and Heinz Decker Institut fur Molekulare Biophysik Johannes Gutenberg Universitat Mainz Germany Keywords Eurypelma hemocyanin micelle phenoloxidase SDS Correspondence E. Jaenicke Institut fur Molekulare Biophysik Johannes Gutenberg Universitat Jakob Welder Weg 26 55128 Mainz Germany Fax 49 6131 3923557 Tel 49 6131 3923570 E-mail Received 2 January 2008 revised 22 January 2008 accepted 25 January 2008 doi Phenoloxidases occur in almost all organisms being essentially involved in various processes such as the immune response wound healing pigmentation and sclerotization in arthropods. Many hemocyanins are also capable of phenoloxidase activity after activation. Notably in chelicerates a phenoloxidase has not been identified in the hemolymph and thus hemocyanin is assumed to be the physiological phenoloxidase in these animals. Although phenoloxidase activity has been shown for hemocyanin from several cheli-cerate species a characterization of the enzymatic properties is still lacking. In this article the enzymatic properties of activated hemocyanin from the tarantula Eurypelma californicum are reported which was activated by SDS at concentrations above the critical micellar concentration. The activated state of Eurypelma hemocyanin is stable for several hours. Dopamine is a preferred substrate of activated hemocyanin. For dopamine a KM value of mM and strong substrate inhibition at high substrate concentrations were observed. Typical inhibitors of catecholoxidase such as L-mimosine kojic acid tyramine phenylthiourea and azide also inhibit the phenoloxidase activity of activated hemocyanin. This indicates that the activated hemocyanin behaves as a normal phenoloxidase. Hemocyanins are oxygen transport proteins in the hemolymph of many arthropod and mollusk species. Although the overall molecular .

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