猪肾中结晶喹啉酸磷酸核糖基转移酶的分离与性质
Isolation and properties of crystalline quinolinate phosphoribosyltransferase from hog kidney.
作者信息
Shibata K, Iwai K
出版信息
Biochim Biophys Acta. 1980 Feb 14;611(2):280-8. doi: 10.1016/0005-2744(80)90063-7.
Crystalline quinolinate phosphoribosyltransferase (nicotinatenucleotide: pyrophosphate phosphoribosyltransferase (carboxylating), EC 2.4.2.19) was isolated from hog kidney and compared with the same enzyme prepared from hog liver. The enzyme preparation was homogeneous as shown by polyacrylamide gel electrophoresis and ultracentrifugation analysis. The enzyme had a molecular weight of 220 000 and the subunit 35 000. The physicochemical properties of the enzyme were: sedimentation coefficient (S200,W), 7.75 . 10(-13) s; difussion coefficient (D200,W), 5.04 . 10(-7) cm2/s; Stokes radius, 62.05 A, frictional ratio (f/f0), 1.62 and isoelectric point (pI), 4.5. The enzyme was stable at 37 degrees C for 30 min between pH 4.5 and 9.5. Enzyme activity was inhibited by various carboxylic acids; however, this inhibition was reversed by raising the Mg2+ concentration. Optimum pH was 5.5, and no detectable amounts of Mg2+, Mn2+, Fe2+, Cu2+, Zn2+ and Ca2+ were found by atomic absorption spectrophotometry. The enzyme was found to contain sugar. Mg2+ was completely replaceable by Mn2+. The reaction mechanism of this enzyme was suggested to be of the 'ping-pong' type. Km values of quinolinic acid and 5-phosphoribosyl 1-pyrophosphate were 4 . 10(-5) and 1.4 . 10(-4) M, respectively.
从猪肾中分离出结晶喹啉酸磷酸核糖基转移酶（烟酰胺核苷酸：焦磷酸磷酸核糖基转移酶（羧化），EC 2.4.2.19），并与从猪肝中制备的同一种酶进行比较。聚丙烯酰胺凝胶电泳和超速离心分析表明，该酶制剂是均一的。该酶的分子量为220000，亚基分子量为35000。该酶的物理化学性质如下：沉降系数（S20，W）为7.75×10⁻¹³ s；扩散系数（D20，W）为5.04×10⁻⁷ cm²/s；斯托克斯半径为62.05 Å，摩擦比（f/f0）为1.62，等电点（pI）为4.5。该酶在37℃下，pH值在4.5至9.5之间可稳定30分钟。各种羧酸可抑制酶活性；然而，提高Mg²⁺浓度可逆转这种抑制作用。最适pH为5.5，原子吸收分光光度法未检测到Mg²⁺、Mn²⁺、Fe²⁺、Cu²⁺、Zn²⁺和Ca²⁺。发现该酶含有糖类。Mg²⁺可被Mn²⁺完全替代。该酶的反应机制被认为是“乒乓”型。喹啉酸和5-磷酸核糖-1-焦磷酸的Km值分别为4×10⁻⁵和1.4×10⁻⁴ M。
Zotero 插件