The reaction of nitrite with the haemocyanin of Astacus leptodactylus.
The reaction of nitrite with the haemocyanin of Astacus leptodactylus.
复制标题
亚硝酸盐与细指星藻血蓝蛋白的反应。
作者：
J. Tahon;D. Van Hoof;C. Vinckier;R. Witters;M. de Ley;R. Lontie
在pH 5.7的亚硝酸盐与脱氧血蓝蛋白的Astacus leptodactylus的反应产生的methaemocyanin在两个单电子步骤中，作为亚硝酸盐还原为NO。这methaemocyanin可以几乎完全再生的厌氧处理与HONH 2，与制备的methaemocyanin与H2 O2。用HONH 2处理氧合血蓝蛋白的活性位点的破坏解释了在空气下的甲基血蓝蛋白的部分再生，因为在HONH 2的自氧化中形成了痕量的H2 O2。亚硝酸盐与脱氧血蓝蛋白的反应速率几乎是与氧合血蓝蛋白的15倍。相对于pH绘制的伪一级速率常数的对数的斜率为-1.0，表明HNO 2是反应物质。甲红蓝素是e.p.r.检测不到，但在g = 2时，在亚硝酸盐与甲红蓝蛋白结合时观察到双核信号。该信号在pKa为6.50时消失，表明可以被亚硝酸根取代的μ-水桥接配体被去质子化为μ-羟基桥接配体，其抵抗被亚硝酸根取代。这三重态的强度。信号允许测定亚硝酸盐与Astacus methaemocyanin活性位点的缔合常数，并在pH 5.7下得到237 M-1的值。亚硝酰血蓝蛋白的亚硝酸盐衍生物的semi-methaemocyanin的一些作者的解释是矛盾的，这种快速反应的亚硝酸盐与铜（I）在脱氧血蓝蛋白和semi-methaemocyanin和低结合常数的亚硝酸盐的活性位点的methaemocyanin。
The reaction of nitrite at pH 5.7 with deoxyhaemocyanin of Astacus leptodactylus yielded methaemocyanin in two one-electron steps, as nitrite was reduced to NO. This methaemocyanin could be almost fully regenerated by an anaerobic treatment with HONH2, in contrast with the methaemocyanin prepared with H2O2. A destruction of active sites on treating oxyhaemocyanin with HONH2 explains the partial regeneration of methaemocyanin under air, as traces of H2O2 are formed in the autoxidation of HONH2. The reaction rate of nitrite with deoxyhaemocyanin is almost 15 times that with oxyhaemocyanin. The slope of -1.0 for the logarithm of the pseudo-first-order rate constants plotted against pH indicates that HNO2 is the reacting species. Methaemocyanin was e.p.r.-undetectable, but a binuclear signal was observed at g = 2 on binding nitrite to methaemocyanin. This signal disappeared with a pKa of 6.50, suggesting that a mu-aquo bridging ligand, which can be replaced by nitrite, is deprotonated to a mu-hydroxo bridging ligand, which resists substitution by nitrite. The intensity of this triplet e.p.r. signal allowed the determination of the association constant of nitrite to the active site of Astacus methaemocyanin and yielded a value of 237 M-1 at pH 5.7. The interpretation by some authors of nitrosylhaemocyanin as a nitrite derivative of semimethaemocyanin is contradicted by this rapid reaction of nitrite with copper(I) in deoxyhaemocyanin and in semi-methaemocyanin and by the low binding constant of nitrite to the active site of methaemocyanin.