Tayeh M A, Madigan M T
Department of Microbiology, Southern Illinois University, Carbondale 62901.
Biochem J. 1988 Jun 1;252(2):595-600. doi: 10.1042/bj2520595.
Purified malate dehydrogenases from four species of non-sulphur purple phototrophic bacteria were examined for their heat-stability, amino acid composition and antigenic relationships. Malate dehydrogenase from Rhodospirillum rubrum, Rhodobacter capsulatus and Rhodomicrobium vannielii (which are all tetrameric proteins) had an unusually high glycine content, but the enzyme from Rhodocyclus purpureus (which is a dimer) did not. R. rubrum malate dehydrogenase was extremely heat-stable relative to the other enzymes, withstanding 65 degrees C for over 1 h with no loss of activity. By contrast, malate dehydrogenase from R. vannielii lost activity above 35 degrees C, and that from R. capsulatus above 40 degrees C. Amino acid compositional relatedness and immunological studies indicated that tetrameric phototrophic-bacterial malate dehydrogenases were highly related to one another, but only distantly related to the tetrameric enzyme from Bacillus. This suggests that, despite differences in their thermal properties, the tetrameric malate dehydrogenases of non-sulphur purple bacteria constitute a distinct biochemical class of this catalyst.
对四种非硫紫色光合细菌的纯化苹果酸脱氢酶进行了热稳定性、氨基酸组成和抗原关系的检测。来自红螺菌、荚膜红细菌和凡氏红微菌（均为四聚体蛋白）的苹果酸脱氢酶具有异常高的甘氨酸含量，但来自紫环菌（二聚体）的酶则没有。相对于其他酶，红螺菌苹果酸脱氢酶具有极高的热稳定性，在65℃下耐受1小时以上且活性无损失。相比之下，凡氏红微菌的苹果酸脱氢酶在35℃以上失去活性，荚膜红细菌的苹果酸脱氢酶在40℃以上失去活性。氨基酸组成相关性和免疫学研究表明，四聚体光合细菌苹果酸脱氢酶彼此高度相关，但与芽孢杆菌的四聚体酶只有远缘关系。这表明，尽管它们的热性质存在差异，但非硫紫色细菌的四聚体苹果酸脱氢酶构成了该催化剂的一个独特生化类别。
