P-Phenylenediamine, mustard

The ability of a chemical to alkylate has been seen to depend on either its ability to form carbonium ions, or transition complexes. The rate at which it achieves this determines the total level of cellular alkylation, since the agent is only in the cell, in most cases, for a relatively short period before it is excreted or metabolized to an inactive derivative, p-phenylenediamine mustard is a very reactive alkylating agent, but can be converted by intracellular acetylases to an N-acetyl derivative whose rate of reaction, i.e. rate of formation of carbonium ions, is much less ... 

A cell with a high acetylase activity would be much less sensitive to p-phenylenediamine mustard than one with no acetylase activity, all other things being equal, since if both compounds remained in the cell for only the same short period of time as is likely, the latter acetylated compound would react far less extensively than the former. 

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