Brodniewicz-Proba T, Buchowicz J
Biochem J. 1980 Oct 1;191(1):139-45. doi: 10.1042/bj1910139.
An enzyme able to catalyse the polymerization of deoxyribonucleotides in a template-independent manner was isolated from dry wheat germ. This activity is associated with a soluble protein which is homogeneous with respect to the molecular weight (approx. 500000) and, under denaturing conditions, dissociates into product of two size classes, 67000 and 45000 daltons respectively. The enzyme-catalysed polymerization can be primed by oligo- as well as poly-deoxyribonucleotides, and is highly efficient (234 nmol/h per mg of finally purified protein) when only one of the four deoxyribonucleoside 5'-triphosphates is present in the incubation mixture. An extension of the 3'-hydroxy termini of polydeoxyribonucleotide chains for approx. 40 nucleotide residues was achieved when non-denatured DNA and [3H]dTTP were used as the primer and substrate respectively. It is concluded that the enzyme isolated from wheat germ shares catalytic properties with the terminal deoxynucleotidyltransferase of mammalian thymus. Unlike that transferase, however, the plant enzyme prefers non-denatured to single-stranded DNA as primer and requires both Mg2+ and Mn2+ ions for maximal activity.
从干小麦胚中分离出一种能够以不依赖模板的方式催化脱氧核糖核苷酸聚合的酶。该活性与一种可溶性蛋白质相关，这种蛋白质在分子量方面是均一的（约500000），并且在变性条件下，分别解离成两种大小类别的产物，即67000和45000道尔顿。酶催化的聚合反应可以由寡聚脱氧核糖核苷酸以及多聚脱氧核糖核苷酸引发，并且当温育混合物中仅存在四种脱氧核苷5'-三磷酸之一时，效率很高（每毫克最终纯化的蛋白质每小时234纳摩尔）。当分别使用非变性DNA和[3H]dTTP作为引物和底物时，多聚脱氧核糖核苷酸链的3'-羟基末端延伸了约40个核苷酸残基。得出的结论是，从小麦胚中分离出的酶与哺乳动物胸腺的末端脱氧核苷酸转移酶具有共同的催化特性。然而，与那种转移酶不同的是，这种植物酶更喜欢以非变性DNA而非单链DNA作为引物，并且需要Mg2+和Mn2+离子才能达到最大活性。
