Synthesis of 5-IASA-UDP-GlcNAc and its use for the photoaffinity labeling of a novel UDP-GlcNAc pyrophosphorylase

Photoreactivable 5-l3-(p-iodoazidosalicylamide)allylJ-UDP-GlcNAc (5-IASA-UDP- -GlcNAc) was synthesized by a four-step procedure and used for photoaffinity labeling of UDP-GlcNAc-dependent enzymes. Upon iodination with 12SI, the compound was successfully applied to probe a purified UDP-GlcNAc pyrophos­phorylase from pig liver. The enzyme was photoinactivated by the probe in the concentration-dependent manner, and was protected by UDP-GlcNAc and, to a lesser extent, by UTP and UDP-GlcCOOH.