School of Life Sciences, The Chinese University of Hong Kong, China.
Environ Toxicol Chem. 2013 Aug;32(8):1882-7. doi: 10.1002/etc.2265. Epub 2013 Jun 27.
Some aquatic organisms can live in contaminated environment due to their adaptable defense mechanism related to their inducible detoxification and excretion. A recent study showed glyceraldehyde-3-phosphate dehydrogenase (GAPDH) can modulate different cellular activities including transcription activation and detoxification. In the present study, the authors report on experiments to test the GAPDH activity of Chironomus riparius toward heavy metals. Glyceraldehyde-3-phosphate dehydrogenase was isolated and purified from C. riparius. The kinetics of the enzyme was measured. The results showed that GAPDH was inhibited by heavy metals including Co(2+) , Cu(2+) , Fe(2+) , Ni(2+) , Pb(2+) , but was activated by zinc ions. The kinetics study of the enzyme showed maximum initial velocity (Vmax) of GAPDH increased by 50%. In addition, the substrate and cofactor affinity increased in the presence of zinc. The GAPDH from C. riparius had maximum activities at pH 8.5 and 37 °C. The protein sequence analysis shows that there are 2 additional cysteine and histidine residues in the conserved region of GAPDH from C. riparius, which is believed to play an important role in the interactions with heavy metals. The results suggest that exposure to zinc could modulate GAPDH, which could be related to response of antioxidant defense to other heavy metals.
一些水生生物由于其与诱导解毒和排泄相关的适应性防御机制，可以在污染环境中生存。最近的一项研究表明，甘油醛-3-磷酸脱氢酶（GAPDH）可以调节包括转录激活和解毒在内的不同细胞活动。在本研究中，作者报告了测试摇蚊（Chironomus riparius）对重金属的 GAPDH 活性的实验。从摇蚊中分离和纯化了甘油醛-3-磷酸脱氢酶。测量了该酶的动力学。结果表明，重金属如 Co(2+)、Cu(2+)、Fe(2+)、Ni(2+)、Pb(2+)抑制 GAPDH，但锌离子激活 GAPDH。该酶的动力学研究表明，GAPDH 的最大初始速度（Vmax）增加了 50%。此外，锌存在时，底物和辅因子的亲和力增加。摇蚊的 GAPDH 在 pH8.5 和 37°C 时具有最大活性。蛋白质序列分析表明，摇蚊 GAPDH 的保守区域有 2 个额外的半胱氨酸和组氨酸残基，这被认为在与重金属的相互作用中起重要作用。结果表明，锌的暴露可能会调节 GAPDH，这可能与抗氧化防御对其他重金属的反应有关。
