Azpilicueta Claudia E, Pena Liliana B, Tomaro María L, Gallego Susana M
Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina.
Redox Rep. 2008;13(1):40-6. doi: 10.1179/135100008X259141.
Catalase (CAT) dismutates the reactive oxygen species H2O2 into water and dioxygen and in plants; it is located in peroxisomes and glyoxysomes. In the present study, we investigated the effect of cadmium (a well-known oxidative stress inducer) on catalase in roots and cotyledons of developing sunflower seedlings, at 10 microM and 100 microM. Although germination was unaltered after 48 h of exposure to 100 microM Cd2+, root length was significantly reduced. CAT activity was also significantly reduced, but this activity was completely restored (10 microM treatment) or even enhanced (100 microM treatment) 24 h later. Although CAT protein abundance remained similar to control in roots and cotyledons of Cd-treated seedlings, cadmium produced CAT protein oxidation, indicating that the mechanism of CAT inactivation by Cd2+ involves oxidation of the protein structure. The transcripts of the four genes described for sunflower (CATA1 to CATA4) increased after cadmium treatment; CATA1 and CATA2 were the most overexpressed in cotyledon and root, respectively. The differential expression of catalase genes in sunflower seedlings under Cd stress might be related to the synthesis of CAT isoforms less sensitive to oxidation, which would prevent enzyme inactivation and H2O2 accumulation.
过氧化氢酶（CAT）可将活性氧物质过氧化氢分解为水和氧气，在植物中，它位于过氧化物酶体和乙醛酸循环体中。在本研究中，我们研究了镉（一种著名的氧化应激诱导剂）在10微摩尔和100微摩尔浓度下对发育中的向日葵幼苗根和子叶中过氧化氢酶的影响。尽管在暴露于100微摩尔镉离子48小时后发芽未受影响，但根长显著缩短。过氧化氢酶活性也显著降低，但24小时后该活性完全恢复（10微摩尔处理）甚至增强（100微摩尔处理）。尽管镉处理的幼苗根和子叶中过氧化氢酶蛋白丰度与对照相似，但镉导致了过氧化氢酶蛋白氧化，这表明镉离子使过氧化氢酶失活的机制涉及蛋白质结构的氧化。向日葵中描述的四个基因（CATA1至CATA4）的转录本在镉处理后增加；CATA1和CATA2分别在子叶和根中表达上调最为明显。镉胁迫下向日葵幼苗中过氧化氢酶基因的差异表达可能与对氧化不太敏感的过氧化氢酶同工型的合成有关，这将防止酶失活和过氧化氢积累。
