REVERSE DIRECTION SUBSTRATE KINETICS AND INHIBITION STUDIES ON 1ST ENZYME OF HISTIDINE BIOSYNTHESIS, ADENOSINE-TRIPHOSPHATE PHOSPHORIBOSYLTRANSFERASE
REVERSE DIRECTION SUBSTRATE KINETICS AND INHIBITION STUDIES ON 1ST ENZYME OF HISTIDINE BIOSYNTHESIS, ADENOSINE-TRIPHOSPHATE PHOSPHORIBOSYLTRANSFERASE
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DOI：
10.1016/0003-9861(76)90560-9
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发表时间：
1976-01-01
影响因子：
3.9
通讯作者：
PARSONS, SM
中科院分区：
文献类型：
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作者：
KLEEMAN, JE;PARSONS, SM
[鼠伤寒沙门氏菌]ATP磷酸核糖基转移酶[EC 2.4.2.17]的初速度稳态底物动力学与生物合成反应方向相反，符合顺序动力学机制。组氨酸对逆反应具有完全的协同抑制作用。产物和替代产物抑制研究阐明结合顺序。交替乘积。。和。-亚甲基ATP相对于n1 -磷酸核糖基-ATP是竞争性的，而相对于PPi是非竞争性的。磷酸核糖基PPi对两种底物均无竞争性。这些数据与生物合成方向反应的数据在定量上与ATP或磷酸核糖基-ATP与游离酶结合的有序Bi-Bi动力学机制一致。
Initial velocity steady-state substrate kinetics for [Salmonella typhimurium] ATP phosphoribosyltransferase [EC 2.4.2.17] were determined in the direction reverse to the biosynthetic reaction and are consistent with a sequential kinetic mechanism. Histidine inhibited the reverse reaction cooperatively and completely. Product and alternate product inhibition studies were conducted to elucidate binding order. The alternate product .beta.,.gamma.-methylene ATP was competitive with respect to N1-phosphoribosyl-ATP and noncompetitive with respect to PPi. Phosphoribosyl PPi was noncompetitive with respect to both substrates. These data and those of the biosynthetic direction reaction are in satisfactory quantitative agreement with the ordered Bi-Bi kinetic mechanism with ATP or phosphoribosyl-ATP binding to free enzyme.