Kruk Jerzy, Jedynak Paweł, Kędracka-Krok Sylwia, Szymańska Renata, Gabruk Michał
Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
Department of Physical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
Antioxidants (Basel). 2024 Feb 29;13(3):301. doi: 10.3390/antiox13030301.
Purification of extracts from the etiolated seedlings of runner bean (), coupled with mass spectrometry analysis of proteins revealed that the enzyme responsible for tocopherol oxidation activity is lipoxygenase, an enzyme known for enzymatic lipid peroxidation of unsaturated lipids. Biochemical analysis of the activity, along with the expression profile of three isoforms (, , ) in various parts of the etiolated seedlings, revealed that was the major isoform expressed in the epicotyls, indicating that this isoform was responsible for the tocopherol oxidation activity; in the primary leaves, besides , the other two isoforms might have also contributed to the activity. The experiments performed in the model systems showed that unsaturated lipids were not required for the tocopherol oxidase activity, but that lipids were necessary to provide an optimal, hydrophobic environment of the substrate for the reaction. The experiments on lipoxygenase and tocopherol oxidase activities in the leaves of light-grown plants during aging and during storage of the extracts from etiolated seedlings showed that the activity of the first reaction decreased considerably faster than the latter, indicating different mechanisms of both reactions performed by the same enzyme. As LOX3 was shown to occur in the apoplast of the related species , the question as to the physiological function of LOX3 in the tocopherol oxidation activity in is discussed.
菜豆黄化幼苗提取物的纯化，结合蛋白质的质谱分析表明，负责生育酚氧化活性的酶是脂氧合酶，一种以催化不饱和脂质的酶促脂质过氧化作用而闻名的酶。对该活性的生化分析，以及三种同工型（、、）在黄化幼苗各部分的表达谱显示，是在上胚轴中表达的主要同工型，表明该同工型负责生育酚氧化活性；在初生叶中，除了外，其他两种同工型可能也对该活性有贡献。在模型系统中进行的实验表明，生育酚氧化酶活性不需要不饱和脂质，但脂质对于为反应提供底物的最佳疏水环境是必需的。对光生长植物叶片在衰老过程中以及黄化幼苗提取物储存期间的脂氧合酶和生育酚氧化酶活性的实验表明，第一个反应的活性下降速度比后者快得多，表明同一酶进行的两种反应具有不同的机制。由于已证明LOX3存在于相关物种的质外体中，因此讨论了LOX3在菜豆生育酚氧化活性中的生理功能问题。
