a, Connolly surface of uPA showing the catalytic triad His 57, Asp 102 and Ser 195 (red) at the bottom, and Arg 35, Arg A37 (blue) at the brim, of the cavity. EGCG, well fitted into this cavity, is shown as a ‘stick model’ in green (C), red (O) and white (H). The calculated energy of intermolecular interaction between EGCG and uPA is −116.81 kcal mol−1; LUDI score, 498; calculated Ki, 1.04×10−5 M. b, Cleavage of Spectrozyme by uPA in the presence of EGCG (inset) from Sigma (blue triangles), and from MayBridge, UK (purple diamonds); amiloride (green squares), and control sample (orange circles). Experimental mixtures (50 mM Tris with 0.01% Tween 80, 0.01% PEG 8000 buffer; pH 8.8) were incubated with 1 μg of uPA and decreasing amounts of inhibitor for 15 min. 100 μl of this mixture was incubated in a 96-well microplate with 50 μl (2.5 mM) Spectrozyme (carbobenzyl-L-(γ)-Glu(α-t-BuO)-Gly-Arg-p-nitroanilide.2C2H5OH from American Diagnostica Inc., Greenwich, Connecticut), for 10 min. Absorbance, which is inversely proportional to the uPA inhibitory activity7, was measured at 405 nm on a microplate reader.