环磷酸腺苷（cAMP）导致S-腺苷-L-高半胱氨酸水解酶失活是由于与酶结合的烟酰胺腺嘌呤二核苷酸（NAD+）解离所致。
Inactivation of S-adenosyl-L-homocysteine hydrolase by cAMP results from dissociation of enzyme-bound NAD+.
作者信息
Hohman R J, Guitton M C, Veron M
出版信息
Proc Natl Acad Sci U S A. 1985 Jul;82(14):4578-81. doi: 10.1073/pnas.82.14.4578.
S-Adenosyl-L-homocysteine hydrolase (EC 3.3.1.1) is inactivated by cAMP and also by 2'-deoxyadenosine, and in both cases, activity is restored by incubating the inactivated enzyme with NAD+. We have previously presented evidence that, despite these similarities, inactivation by these two ligands proceeds by different mechanisms. We have now used a fluorescence technique to quantitate enzyme-bound NAD+ and NADH on S-adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum, and we have confirmed that cAMP and 2'-deoxyadenosine inactivate by different mechanisms. Whereas inactivation by 2'-deoxyadenosine is due to reduction of the enzyme-bound NAD+ to NADH, incubation of S-adenosyl-L-homocysteine hydrolase with cAMP results in dissociation of the enzyme-bound NAD+. The dissociation is reversible, and reactivation likely occurs by restoration of the initial NAD+ content. This reversible inactivation by cAMP may be a mechanism of controlling biological methylation reactions by adjusting intracellular concentrations of S-adenosyl-L-homocysteine through action of S-adenosyl-L-homocysteine hydrolase.
S-腺苷-L-高半胱氨酸水解酶（EC 3.3.1.1）可被环磷酸腺苷（cAMP）以及2'-脱氧腺苷灭活，在这两种情况下，通过将失活的酶与烟酰胺腺嘌呤二核苷酸（NAD+）一起孵育可恢复其活性。我们之前已提出证据表明，尽管存在这些相似之处，但这两种配体的灭活作用是通过不同机制进行的。我们现在使用一种荧光技术来定量盘基网柄菌的S-腺苷-L-高半胱氨酸水解酶上结合的NAD+和烟酰胺腺嘌呤二核苷酸（NADH），并且我们已证实cAMP和2'-脱氧腺苷通过不同机制灭活。2'-脱氧腺苷导致的灭活是由于酶结合的NAD+被还原为NADH，而将S-腺苷-L-高半胱氨酸水解酶与cAMP一起孵育会导致酶结合的NAD+解离。这种解离是可逆的，重新激活可能是通过恢复初始的NAD+含量来实现的。cAMP引起的这种可逆性灭活可能是一种通过S-腺苷-L-高半胱氨酸水解酶的作用调节细胞内S-腺苷-L-高半胱氨酸浓度来控制生物甲基化反应的机制。
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