菠菜中的乙醇酸氧化酶是一个同工酶

乙醇酸氧化酶（ＥＣ．１．１．３．１５．ＧＯ）是光呼吸途径的关键酶，降低其活性可提高Ｃ３植物如水稻的产量，在目前中国乃至世界人口不断增加和可耕种土地日益减少的情况下，对ＧＯ的研究具有重要的理论意义和实际应用价值．在光呼吸途径被提出后的几十年间，人们对如...

Spinach Glycolate Oxidase is An Isozyme

glycolate oxidase was considered a homogeneous enzyme consisted of FMN and one kind of subunit before, but this view could not explain why three different isoelectric points coexisted in different plants. Using the steps of ammonium sulfate fractionation and Sephadex G 25 chromatography,the protein with glycolate oxidase activity in the spinach crude protein was prepared from the second protein peak on DEAE cellulose chromatography,among which the glycolate oxidase, expressed as COⅢ (Sp.act:14 U·mg -1 ·min -1 ),could not migrate in 4%_20% native PAGE under pH8.3 buffer system, so its p I was about pH8.3. From this protein, another glycolate oxidase, expressed as GO Ⅰ(specific activity:1 6 U·mg -1 ·min -1 ) showed only one band in SDS PAGE, and was purified on the Sepharose 6B chromatography which migrated towards anode with the molecular weight of 470 and 280 kD assayed in the same native PAGE, so its p I was smaller than pH8.3. By the 8% native PAGE Western blot in which GO Ⅰ antibody was uesd, the third glycolate oxidase, expressed as GO Ⅱ, was confirmed in the spinach crude protein and migrated towards cathode under the same pH8.3 buffer system, its p I was about pH9.4 detected by IEF and glycolate oxidase activity stain, GO Ⅰ and GO Ⅲ were also confirmed in the spinach crude protein by the same Western blot.Based on the results above, a new theory was put forward that spinach glycolate oxidase was an isozyme consisted of GO Ⅰ(p I <8.3),GOⅡ(p I ≈9.4),and GOⅢ(p I ≈8.3).They showed different p I , glycolate oxidase activity, and stability.There were immunity among them.GOⅢ could turn into GOⅠ.GOⅠ consisted of FMN and one kind of subunit, but the subunit components of GO Ⅱand GOⅢ had never been discussed.