Hohman R J, Veron M
FEBS Lett. 1984 Jan 9;165(2):265-8. doi: 10.1016/0014-5793(84)80182-9.
Purified S-adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum is inactivated when incubated at 25 degrees C with cAMP. Half maximal velocity of the inactivation process occurs at 10 microM cAMP. Catalytic activity is fully restored by further incubation with NAD+, but not with NADP+ or NADH. The enzyme must be preincubated with cAMP or NAD+ to induce inactivation or reactivation, respectively, since neither of these ligands has an effect on the active or inactive enzyme when added directly to the assay. These results suggest a role for cAMP and NAD+ in the regulation of cellular methylation reactions by altering the level of S-adenosyl-L-homocysteine via S-adenosyl-L-homocysteine hydrolase.
来自盘基网柄菌的纯化S-腺苷-L-高半胱氨酸水解酶在25摄氏度下与环磷酸腺苷（cAMP）一起孵育时会失活。失活过程的半数最大速度出现在10微摩尔的环磷酸腺苷浓度下。通过与烟酰胺腺嘌呤二核苷酸（NAD+）进一步孵育，催化活性可完全恢复，但与烟酰胺腺嘌呤二核苷酸磷酸（NADP+）或烟酰胺腺嘌呤二核苷酸（NADH）一起孵育则不能恢复。该酶必须分别预先与环磷酸腺苷或烟酰胺腺嘌呤二核苷酸孵育以诱导失活或再激活，因为当直接添加到测定中时，这些配体对活性或无活性的酶均无影响。这些结果表明，环磷酸腺苷和烟酰胺腺嘌呤二核苷酸通过S-腺苷-L-高半胱氨酸水解酶改变S-腺苷-L-高半胱氨酸的水平，从而在细胞甲基化反应的调节中发挥作用。
