Schultes B C, Fischbach E, Dahlmann N
Institut für Klinische Biochemie, Universität Bonn, Germany.
Biol Chem Hoppe Seyler. 1992 May;373(5):237-47. doi: 10.1515/bchm3.1992.373.1.237.
Two different enzymes capable of hydrolysing dTTP to the corresponding diphosphate were purified from human serum in order to investigate their enzymatic properties. A specific dTTPase was purified to apparent homogeneity with a purification factor of ca. 10,000 and showed a molecular mass of 46,000 Da, consisting of two identical subunits. This enzyme revealed an isoelectric point of 5.8 and a Km value of 38 microM. The other enzyme showed substrate specificity for dTTP and dCTP and was purified with a factor of ca. 5,000. It seems to be a multifunctional enzyme of one subunit (96,000 Da) with two different catalytic sites for dTTP and dCTP. The isoelectric point was 5.2, the Km values were 20 microM for dTTP and 17 microM for dCTP, respectively. Both enzymes were sensitive to inorganic phosphate, but the dTTPase to a minor extent. In contrast to the dCTPase-dTTPase, the dTTPase was strongly inhibited by ZnSO4. Physico-chemical and biochemical data suggest the purification of two different enzymes.
为了研究其酶学性质，从人血清中纯化出两种能够将dTTP水解为相应二磷酸的不同酶。一种特异性dTTP酶被纯化至表观均一，纯化因子约为10,000，分子量为46,000 Da，由两个相同的亚基组成。该酶的等电点为5.8，Km值为38 μM。另一种酶对dTTP和dCTP表现出底物特异性，纯化因子约为5,000。它似乎是一种单亚基（96,000 Da）的多功能酶，具有针对dTTP和dCTP的两个不同催化位点。等电点为5.2，dTTP的Km值为20 μM，dCTP的Km值分别为17 μM。两种酶都对无机磷酸盐敏感，但dTTP酶的敏感程度较小。与dCTP酶-dTTP酶不同，dTTP酶受到ZnSO4的强烈抑制。物理化学和生化数据表明纯化出了两种不同的酶。
