牛脳ペルオキシソームの D-アスパラギン酸オキシダーゼに関する研究

抄録

D-aspartate oxidase (D-AspO : EC 1.4.3.1.) is a flavoprotein that catalyzes the oxidative deamination of dicarboxylic D-amino acids with the production of H_2O_2, NH_3, and corresponding α-keto acid. D-AspO has been found in many mammalian tissues, showing that D-AspO differs from D-amino-acid oxidase (DAO : EC 1.4.3.3) and is located in the peroxisomes of mammalian liver and kidney. However, there is no report on the properties of D-AspO in mammalian brain. Therefore, we examined the properties of DAO and D-AspO in bovine brain, and highly purified D-AspO from fetal bovine brain stem of 10-month-old. 1) The D-AspO activity was detected in all tissues of bovine tested. Strikingly, a very high activity of D-AspO was detected in brain stem, and the activity increased with growth of fetal bovine. 2) D-AspO was located in the peroxisomes of brain tissues in fetal and post natal bovine. 3) Peroxisomes in bovine brain tissues were microperoxisomes and differed from peroxisomes of liver and kidney in density. 4) Very low DAO activities were detected in all tissues of bovine brain tested. 5) The D-AspO activity increased following growth of fetal bovine. 6) D-AspO purified from brain stem of 10-month-old fetal bovine consists of four identical subunits with a molecular weight of 29, 000Da. 7) The enzyme was highly specific towards NMDA and D-aspartate as substrate. On the basis of the above results, D-AspO may be used as a peroxisomal marker enzyme in the brain.