Purification, Characterization, and Overexpression of Psychrophilic and Thermolabile Malate Dehydrogenase of a Novel Antarctic Psychrotolerant,<i>Flavobacterium frigidimaris</i>KUC-1
作者:Tadao OIKAWA、Noriko YAMAMOTO、Koji SHIMOKE、Shinichi UESATO、Toshihiko IKEUCHI、Toru FUJIOKA
DOI:10.1271/bbb.69.2146
日期:2005.1
We purified the psychrophilic and thermolabile malate dehydrogenase to homogeneity from a novel psychrotolerant, Flavobacterium frigidimaris KUC-1, isolated from Antarctic seawater. The enzyme was a homotetramer with a molecular weight of about 123 k and that of the subunit was about 32 k. The enzyme required NAD(P)+ as a coenzyme and catalyzed the oxidation of L-malate and the reduction of oxalacetate specifically. The reaction proceeded through an ordered bi–bi mechanism. The enzyme was highly susceptible to heat treatment, and the half-life time at 40 °C was estimated to be 3.0 min. The kcat/Km (μM−1·s−1) values for L-malate and NAD+ at 30 °C were 289 and 2,790, respectively. The enzyme showed pro-R stereospecificity for hydrogen transfer at the C4 position of the nicotinamide moiety of the coenzyme. The enzyme contained 311 amino acid residues and much lower numbers of proline and arginine residues than other malate dehydrogenases.
我们从南极海水中分离出的一种新型心理耐受性黄杆菌(Flavobacterium frigidimaris KUC-1)中纯化出了具有心理亲和性和热稳定性的苹果酸脱氢酶。该酶是一种同源四聚体,分子量约为 123 k,亚基分子量约为 32 k。该酶需要 NAD(P)+ 作为辅酶,专门催化 L-苹果酸的氧化和草酰乙酸的还原。反应通过有序的双生物机制进行。该酶极易受热处理影响,在 40 °C 时的半衰期估计为 3.0 分钟。30 °C时,L-苹果酸和NAD+的kcat/Km(μM-1-s-1)值分别为289和2,790。该酶对辅酶烟酰胺分子 C4 位的氢转移具有亲 R 立体特异性。该酶含有 311 个氨基酸残基,脯氨酸和精氨酸残基的数量远低于其他苹果酸脱氢酶。