Isolation and characterization of peroxisomes from diatoms
Isolation and characterization of peroxisomes from diatoms
复制标题
硅藻过氧化物酶体的分离和表征
作者：
U. Winkler;H. Stabenau
过氧化物酶体通过梯度离心从两种不同的硅藻中分离：光滑菱形藻（Pennales亚组）和Thalassiosira fluviatilis（Centrales亚组）。在这两个细胞器不能过氧化氢酶或任何H2 O2形成氧化酶被证明。存在于过氧化物酶体中的乙醇酸氧化酶是一种也能够氧化l-乳酸的脱氢酶。过氧化物酶体还含有乙醛酸酶体标记物异柠檬酸裂合酶和苹果酸合酶。然而，脂肪酸β-氧化途径的酶仅位于线粒体中。线粒体另外具有谷氨酸-乙醛酸氨基转移酶和乙醇酸脱氢酶，其不同于过氧化物酶体乙醇酸脱氢酶，因为其优选利用d-乳酸作为替代底物。羟基丙酮酸还原酶和乙醛酸碳连接酶没有发现在细胞的硅藻。通过培养光滑菱形藻，可以证明，将通气混合物中的CO2浓度从2%降低到0.03%，并将辐照度从40 μmol quanta · m-2 · s-1增加到250 μmol quanta · m-2 · s-1，导致过氧化物酶体酶活性的增加。此外，β-氧化途径的酶活性增加。然而，线粒体乙醇酸脱氢酶和氨基转移酶并没有改变他们的活动在这些条件下。总结所有的结果，这是假设，有两个不同的途径代谢的乙醇酸在硅藻。
Peroxisomes were isolated by gradient centrifugation from two different diatoms: Nitzschia laevis (subgroup of Pennales) and Thalassiosira fluviatilis (subgroup of Centrales). In neither of these organelles could catalase or any H2O2-forming oxidase be demonstrated. The glycolate-oxidizing enzyme present in the peroxisomes is a dehydrogenase capable of oxidizing l-lactate as well. The peroxisomes also contain the glyoxysomal markers isocitrate lyase and malate synthase. However, enzymes of the fatty-acid β-oxidation pathway are located exclusively in the mitochondria. The mitochondria additionally possess glutamate-glyoxylate aminotransferase and a glycolate dehydrogenase which differs from the peroxisomal glycolate dehydrogenase since it preferably utilizes d-lactate as an alternative substrate. Hydroxypyruvate reductase and glyoxylate carboligase were not found in the cells of either diatom. By culturing Nitzschia laevis it could be demonstrated that decreasing the CO2 concentration in the aeration mixture from 2% to 0.03% and increasing the irradiance from 40 to 250 μmol quanta · m−2 · s−1 resulted in an increase of all peroxisomal enzyme activities. In addition, enzyme activities of the β-oxidation pathway were increased. However, mitochondrial glycolate dehydrogenase and aminotransferase did not alter their activities under these conditions. Summarizing all results, it is postulated that there are two different pathways for the metabolism of glycolate in the diatoms.