期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2007
卷号：104
期号：1
页码：83-86
DOI：10.1073/pnas.0609644104
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Alkyl sulfate monoesters are involved in cell signaling and structure. Alkyl sulfates are also present in many commercial detergents. Here, we show that monomethyl sulfate acts as an efficient alkylating agent in water, reacting spontaneously with oxygen nucleophiles >100-fold more rapidly than do alkylsulfonium ions, the usual methyl donors in living organisms. These reactions of methyl sulfate, which are much more rapid than its hydrolysis, are insensitive to the nature of the attacking nucleophile, with a Bronsted [beta]nuc value of -0.01. Experiments at elevated temperatures indicate a rate constant of 2 x 10-11 s-1 for the uncatalyzed hydrolysis of methyl sulfate at 25{degrees}C (t1/2 = 1,100 y), corresponding to a rate enhancement of {approx}1011-fold by a human alkylsulfatase. Equilibria of formation of methyl sulfate from methanol and sodium hydrogen sulfate indicate a group transfer potential ({Delta}G'pH7) of -8.9 kcal/mol for sulfate ester hydrolysis. The magnitude of that value, involving release of the strong acid HSO[IMG]f1.gif" ALT="Formula" BORDER="0">, helps to explain the need for harnessing the free energy of hydrolysis of two ATP molecules in activating sulfate for the biosynthesis of sulfate monoesters. The "energy-rich" nature of monoalkyl sulfate esters, coupled with their marked resistance to hydrolysis, renders them capable of acting as sulfating or alkylating agents under relatively mild conditions. These findings raise the possibility that, under appropriate circumstances, alkyl groups may undergo transfer from alkyl sulfate monoesters to biological target molecules.
关键词：group transfer potential ; methyl transfer ; sulfate monoester
