Chattoraj-Bhattacharyya S, Majumder A L
Department of Botany, Bose Institute, Calcutta, India.
Arch Biochem Biophys. 1995 Jan 10;316(1):63-9. doi: 10.1006/abbi.1995.1010.
Purified fish and rat brain FruP2ase(s) are stimulated by a number of chelators, viz., histidine, EDTA, citrate, imidazole, and a number of histidine analogues. These also impart 5'-AMP sensitivity to the otherwise insensitive enzyme. Beyond 3 mM concentration, histidine inhibits the enzyme activity, which can be prevented by Mn2+. Atomic absorption spectrophotometry showed the presence of 5-6 mol of Mn2+ and Zn2+ bound to both fish and rat brain FruP2ase, which can be removed by exhaustive EDTA-dialysis. The EDTA-dialyzed brain FruP2ase records an absolute Mn2+ requirement and 5'-AMP sensitivity without any chelator treatment. The 5'-AMP sensitivity of such enzyme is abolished by prior incubation with Zn2+. The Zn(2+)-treated brain FruP2ase fails to bind to a Blue-Sepharose column, in contrast to that seen using the untreated enzyme. These results suggest that rat and fish brain FruP2ase(s) are actually Mn(2+)- and Zn(2+)-containing proteins with Zn2+ bound at or near the nucleotide-binding site.
纯化的鱼脑和大鼠脑果糖二磷酸酶（FruP2ase）受到多种螯合剂的刺激，即组氨酸、乙二胺四乙酸（EDTA）、柠檬酸盐、咪唑以及多种组氨酸类似物。这些螯合剂还赋予原本不敏感的酶对5'-单磷酸腺苷（5'-AMP）的敏感性。浓度超过3 mM时，组氨酸会抑制酶活性，而锰离子（Mn2+）可以防止这种抑制。原子吸收分光光度法表明，鱼脑和大鼠脑FruP2ase均结合有5 - 6摩尔的Mn2+和锌离子（Zn2+），通过彻底的EDTA透析可以将它们去除。经EDTA透析的脑FruP2ase在不进行任何螯合剂处理的情况下记录到对Mn2+的绝对需求和对5'-AMP的敏感性。这种酶对5'-AMP的敏感性在预先用Zn2+孵育后会被消除。与未处理的酶相比，经Zn2+处理的脑FruP2ase无法与蓝琼脂糖柱结合。这些结果表明，大鼠脑和鱼脑FruP2ase实际上是含Mn2+和Zn2+的蛋白质，其中Zn2+结合在核苷酸结合位点或其附近。
