Studies On The Biochemical Comparison Of Phenoloxidase From The Humoral Fluid And Epidermal Mucus Of Amphioxus Branchiostoma Belcheri Tsingtauense

The enzyme phenoloxidase (PO), which is also named as Tyrosinase, is a Cu-dependent enzyme has been testified to be present widely in both invertebrates and vertebrates. It exists in the invertebrates as a zymogen, which is named as proPO, participates the immune reaction widely.The humoral fluid and epidermal mucus from Amphioxus Branchiostoma belcheri tsingtauense were abstracted and used as the resource of PO and proPO after the preparatory purification with (NH₄)₂SO₄. Sorts of biochemical approaches are used to study and compare the characters of PO from the different tissues of the Amphioxus for the first time.L-DOPA is used as substrate and different activating and inhibiting factors have been added to the mixture. It reveals that Ca²⁺, Mg²⁺, SDS, Trypsin, LPS and Zs could activate both the two kinds of PO while Cu²⁺, PTU, STI and EDTA could inhibit their activity heavily, Zn²⁺ could promote the activity slightly and EGTA could inhibit them slightly, further more the enzyme activity inhibited by EDTA could be resumed by adding additional Ca²⁺. The result demonstrates that PO exists in the humoral fluid and mucus in the style of proPO and they possess similar activated and inhibited capability.It is testified that the optimum temperature, optimum pH and optimum substrate is 35℃, pH7.5, dopamine and 45℃, pH 9, dopamine also for the PO in humoral fluid and mucus, respectively.