Switch between tyrosinase and catecholoxidase activity of scorpion hemocyanin by allosteric effectors |
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Authors: | Nillius Dorothea Jaenicke Elmar Decker Heinz |
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Affiliation: | Institut für Molekulare Biophysik der Johannes Gutenberg Universit?t Mainz, Jakob-Welder-Weg 26, Mainz, Germany. |
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Abstract: | Phenoloxidases and hemocyanins have similar type 3 copper centers although they perform different functions. Hemocyanins are oxygen carriers, while phenoloxidases (tyrosinase/catecholoxidase) catalyze the initial step in melanin synthesis. Tyrosinases catalyze two subsequent reactions, whereas catecholoxidases catalyze only the second one. Recent results indicate that hemocyanins can also function as phenoloxidases and here we show for the first time that hemocyanin can be converted to phenoloxidase. Furthermore, its substrate specificity can be switched between catecholoxidase and tyrosinase activity depending on effectors such as hydroxymethyl-aminomethan (Tris) and Mg(2+)-ions. This demonstrates that substrate specificity is not caused by a chemical modification of the active site. |
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Keywords: | Ty, tyrosinase CO, catecholoxidase Hc, hemocyanin MBTH, 3-methyl-2-benzo-thiazolinone-hydrazone SDS, sodium dodecylsulfate Tris, hydroxymethyl-aminomethan |
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