Rao K N
Radiation Biology and Biochemistry Division, Bhabha Atomic Research Centre, Bombay, India.
Indian J Biochem Biophys. 1994 Apr;31(2):138-42.
Thymidylate synthase (5,10-methylenetetrahydrofolate: deoxyuridylate C-methyltransferase, EC 2.1.1.45) from Lactobacillus leichmannii was completely inactivated after 5 min of heat treatment at 55 degrees C. A remarkable synergistic effect with no loss in activity was noted when 10(-3) M dUMP was added to the enzyme before subjecting to heat treatment. The enzyme got activated in the presence of 2-mercaptoethanol (75 mM) and inhibited by pCMB (I50 = 5 microM). It had 2 free sulfhydryl groups and a single disulfide bond. The two identical subunits of the 74 kDa dimer were possibly bonded by a single disulfide linkage. It had a total of 652 amino acids with methionine as the amino-terminal and alanine as the carboxy-terminal amino acid residues. The carboxy-terminal end-group alanine was preceded by valine, lysine and proline sequentially in that order.
来自莱氏乳杆菌的胸苷酸合酶（5,10-亚甲基四氢叶酸：脱氧尿苷酸C-甲基转移酶，EC 2.1.1.45）在55℃热处理5分钟后完全失活。在热处理前向酶中加入10⁻³M脱氧尿苷一磷酸（dUMP）时，观察到显著的协同效应且活性没有损失。该酶在2-巯基乙醇（75mM）存在下被激活，而被对氯汞苯甲酸（pCMB）抑制（半数抑制浓度I50 = 5μM）。它有2个游离巯基和1个二硫键。74kDa二聚体的两个相同亚基可能通过一个二硫键相连。它共有652个氨基酸，氨基末端为甲硫氨酸，羧基末端氨基酸残基为丙氨酸。羧基末端的丙氨酸之前依次是缬氨酸、赖氨酸和脯氨酸。
