A Cu(II)–[di(2-methylpyridyl)methylamino]coumarin fluorescence turn-on sensor (Cu-1b) is designed to detect phosphate ions with Kass = 1.4 × 105 M−1 in HEPES buffer. Cu-1b is applied to probe the GlgE-catalyzed maltose-transfer reaction of α-maltose-1-phosphate to α-1,4-glucan with concomitant release of phosphate ions in Mycobacterium tuberculosis.
