Wache H, Böhme I, Sorger H, Nilius R
Klinik und Poliklinik für Innere Medizen, Martin-Luther-Universität Halle-Wittenberg.
Biomed Biochim Acta. 1990;49(10):979-89.
A procedure to separate the isozymes E1 and E2 of aldehyde dehydrogenase (ALDH, aldehyde: NAD oxidoreductase, EC 1.2.1.3) from human liver, avoiding 5'-AMP-Sepharose, was worked out. It results in fairly purified isozymes. The isoelectric points could be re-estimated for E1 at pH 5.21 +/- 0.04 and for E2 at pH 4.90 +/- 0.05. The pH-optimum of both the isozymes is dependent on the buffer used, the best buffer being sodium pyrophosphate/HCI. In this buffer the enzyme activity is also dependent on ionic strength. Malondialdehyde (MDA), at concentrations which are found in patient serum, is converted by the ALDH. The Km-values of this reaction are 1.71 mmol/l for MDA and 0.19 mmol/l for NAD (E1) and 0.21 mmol/l for MDA and 0.24 mmol/l for NAD (E2) resp. The highest rates of conversion are reached at concentrations of 0.08 mmol/l MDA (E1) and 0.16 mmol/l MDA (E2). At higher concentrations of MDA substrate excess inhibition is observed (Kss = 0.17 mmol/l for E1 and 0.20 mmol/l for E2).
已制定出一种从人肝脏中分离醛脱氢酶（ALDH，醛：NAD氧化还原酶，EC 1.2.1.3）的同工酶E1和E2的方法，该方法避免使用5'-AMP-琼脂糖。此方法可得到相当纯化的同工酶。重新估算出E1的等电点为pH 5.21±0.04，E2的等电点为pH 4.90±0.05。两种同工酶的最适pH值取决于所使用的缓冲液，最好的缓冲液是焦磷酸钠/盐酸。在此缓冲液中，酶活性也取决于离子强度。丙二醛（MDA）在患者血清中的浓度下可被ALDH转化。该反应的Km值，对于MDA，E1为1.71 mmol/l，NAD为0.19 mmol/l；对于E2，MDA为0.21 mmol/l，NAD为0.24 mmol/l。在MDA浓度为0.08 mmol/l（E1）和0.16 mmol/l（E2）时达到最高转化率。在较高的MDA浓度下，观察到底物过量抑制现象（E1的Kss = 0.17 mmol/l，E2的Kss = 0.20 mmol/l）。
