Yoshino M, Obata T, Sho S, Kinemuchi H
Jpn J Pharmacol. 1984 Jun;35(2):105-15. doi: 10.1254/jjp.35.105.
The present study was undertaken to clarify the enzymic and molecular properties of monoamine oxidase (MAO) in carp brain. In particular, its sensitivities to selective MAO inhibitors, kinetic properties and molecular weight were compared with those of the enzyme in carp liver. The selective and potent MAO-A and MAO-B inhibitors FLA 788(+), FLA 336(+), MD 780236 and benzylcyanide caused dose-dependent inhibitions of MAO activity in both carp brain and liver; the inhibition curves were all single-sigmoidal, and the degrees of inhibition of the activities towards 5-hydroxytryptamine (5-HT, selective MAO-A substrate), tyramine (substrate for both forms of MAO) and beta-phenylethylamine (PEA, selective MAO-B substrate) were similar. This was also the case for inhibition of activity in carp brain by the irreversible and selective MAO-A and MAO-B inhibitors clorgyline and I-deprenyl, indicating the presence in both preparations of a single MAO which differs from either form of MAO. Studies on the substrate specificities and Km values for these three substrates and the inhibitory effects of some compounds suggested that the enzymic characters of MAO in carp preparations were similar and that these enzymes might be FAD-containing enzymes, like MAO in various mammals. By labelling the preparations with radioactive pargyline and then subjecting them to sodium dodecyl sulfate electrophoresis, the apparent molecular weights of carp brain and liver MAO were estimated as 60,000 daltons. The same value was also obtained for rat brain and liver mitochondrial MAO-B. These results indicate that by the present definitions of MAO-A and MAO-B, MAO in carp brain and liver is similar to, but distinct from, both these forms of MAO.
本研究旨在阐明鲤鱼脑中单胺氧化酶（MAO）的酶学和分子特性。特别将其对选择性MAO抑制剂的敏感性、动力学特性和分子量与鲤鱼肝脏中的该酶进行了比较。选择性强效MAO - A和MAO - B抑制剂FLA 788(+)、FLA 336(+)、MD 780236和苄基氰对鲤鱼脑和肝脏中的MAO活性均产生剂量依赖性抑制；抑制曲线均为单S形，对5 - 羟色胺（5 - HT，选择性MAO - A底物）、酪胺（两种形式MAO的底物）和β - 苯乙胺（PEA，选择性MAO - B底物）的活性抑制程度相似。不可逆选择性MAO - A和MAO - B抑制剂氯吉兰和L - 司来吉兰对鲤鱼脑活性的抑制情况也是如此，这表明两种制剂中均存在一种与MAO的两种形式不同的单一MAO。对这三种底物的底物特异性、Km值以及一些化合物的抑制作用的研究表明，鲤鱼制剂中MAO的酶学特性相似，且这些酶可能像各种哺乳动物中的MAO一样是含FAD的酶。通过用放射性帕吉林标记制剂，然后进行十二烷基硫酸钠电泳，估计鲤鱼脑和肝脏MAO的表观分子量为60,000道尔顿。大鼠脑和肝脏线粒体MAO - B也得到了相同的值。这些结果表明，根据目前对MAO - A和MAO - B的定义，鲤鱼脑和肝脏中的MAO与这两种形式的MAO相似，但又有所不同。
