Kulys Juozas, Bratkovskaja Irina, Vidziunaite Regina
Department of Enzyme Chemistry, Institute of Biochemistry, Mokslininku 12, LT-08662 Vilnius, Lithuania.
Biotechnol Bioeng. 2005 Oct 5;92(1):124-8. doi: 10.1002/bit.20610.
The kinetics of potassium triiodide (KI(3)) formation during fungal laccase action was investigated in presence of methyl syringate (MS). The recombinant forms of Polyporus pinsitus (rPpL), Myceliophthora thermophila (rMtL), Coprinus cinereus (rCcL), and Rhizoctonia solani (rRsL) laccases were used. The triiodide formation rate reached 6.1, 5.5, 6.0, and 2.1 microM/min at saturated rPpL, rCcL, rRsL, and rMtL concentration, respectively, in acetate buffer solution pH 5.5 and in presence of 10 microM of MS and 1 mM of potassium iodide. The triiodide formation rate increased if pH decreased from 6.5 to 4.5. The scheme of laccase-catalysed iodide oxidation includes stadium of MS interaction with oxidized laccase with concomitant production of MS(ox). The reaction of MS(ox) with iodide produced triiodide. The turnover number of MS was 93 and 44 at pH 5.5 for rPpL and rMtL, respectively. The scheme also contained a stadium of reversible reduction of laccase active centre with the mediator explaining the different saturation rate of triiodide production. The fitting kinetic data revealed that the reversibility of the reaction increased for laccases containing lower redox potential of copper type I.
在丁香酸甲酯（MS）存在的情况下，研究了真菌漆酶作用过程中三碘化钾（KI(3)）形成的动力学。使用了松杉灵芝（rPpL）、嗜热毁丝霉（rMtL）、灰盖鬼伞（rCcL）和立枯丝核菌（rRsL）漆酶的重组形式。在pH 5.5的醋酸盐缓冲溶液中，在10 μM MS和1 mM碘化钾存在的情况下，当rPpL、rCcL、rRsL和rMtL浓度饱和时，三碘化碘的形成速率分别达到6.1、5.5、6.0和2.1 μM/min。如果pH从6.5降至4.5，三碘化碘的形成速率会增加。漆酶催化碘化物氧化的过程包括MS与氧化型漆酶相互作用并伴随产生MS(ox)的阶段。MS(ox)与碘化物反应生成三碘化碘。在pH 5.5时，rPpL和rMtL的MS周转数分别为93和44。该过程还包括漆酶活性中心与介质可逆还原的阶段，这解释了三碘化碘产生的不同饱和速率。拟合动力学数据表明，对于含有较低I型铜氧化还原电位的漆酶，反应的可逆性增加。
