Hydroxamic acids are metal-chelating compounds that show important biological activity including anti-tumor effects. We have recently engineered the transketolase from Geobacillus stearothermopilus (TKgst) to convert benzaldehyde as a non-natural acceptor substrate. Realizing the structural and electronic similarity to nitrosobenzene, we studied the TK-catalyzed conversion of nitrosoarenes to yield N-arylated hydroxamic acids. Here we demonstrate that wild-type and variants of this versatile TKgst enzyme indeed induce the rapid biocatalytic conversion of variously p-, m- and o-substituted nitrosoarenes to produce a variety of corresponding N-aryl hydroxamic acids via creation of a carbon-nitrogen instead of a carbon-carbon bond. Further structural modifications can be introduced by varying the donor component, such as hydroxypyruvate or pyruvate.