Fernley R T, Lentz S R, Bradshaw R A
Biosci Rep. 1981 Jun;1(6):497-507. doi: 10.1007/BF01121583.
Escherichia coli malate dehydrogenase has been isolated in homogeneous form by a procedure employing chromatography on DEAE-cellulose, 5-'AMP-Sepharose, and Sephacryl-200. It is composed of two identical polypeptide chains each of Mr = 32 500. Like porcine mitochondrial malate dehydrogenase, it is devoid of tryptophan, but otherwise it is not particularly more similar in composition to one of the eukaryotic isozymes than to the other. However, amino-terminal sequence analysis of the first 36 residues shows remarkable similarity of the bacterial and mitochondrial enzymes (69% identical residues) in contrast to the cytoplasmic form (27%). The two porcine heart enzymes are identical in 24% of the positions compared. These results clearly establish that all three forms of malate dehydrogenase have evolved from a common precursor and that the prokaryotic and mitochondrial forms have retained sequences that are much closer to the ancestral one than the cytoplasmic enzyme. These findings appear to further substantiate the endosymbiotic hypothesis for the origin of the mitochondrion.
通过使用DEAE - 纤维素、5'-AMP - 琼脂糖和Sephacryl - 200进行色谱分析的方法，已将大肠杆菌苹果酸脱氢酶分离为均一形式。它由两条相同的多肽链组成，每条链的Mr = 32500。与猪线粒体苹果酸脱氢酶一样，它不含色氨酸，但在组成上，它与一种真核同工酶的相似性并不特别高于另一种。然而，对前36个残基的氨基末端序列分析表明，细菌和线粒体酶具有显著的相似性（69%的相同残基），而与细胞质形式相比则为27%。相比之下，两种猪心脏酶在24%的位置上是相同的。这些结果清楚地表明，苹果酸脱氢酶的所有三种形式都从一个共同的前体进化而来，并且原核和线粒体形式保留了比细胞质酶更接近祖先序列的序列。这些发现似乎进一步证实了线粒体起源的内共生假说。
