Quercetin inhibits whilst methylene blue enhances TbHsp70.c-Tbj2 activity. The effect of quercetin (A) and MB (B) on the basal and Tbj2-stimulated ATPase activity of TbHsp70.c and TcHsp70B was investigated. Inorganic phosphate released by ATP in the presence of each Hsp70 was monitored by direct calorimetry at 595 nm wavelength. TbHsp70.c, TcHsp70B, and Tbj2 concentrations were maintained at 0.4 µM, and ATP was present in all reactions at 600 µM (A). Quercetin was present in the reactions as indicated at 30 µM. The effect of MB on the basal ATPase activity of TbHsp70.c and TbHsp70.c in partnership with Tbj2 was investigated (B). TbHsp70.c and Tbj2 concentrations were kept constant at 1 µM and ATP was present in all reactions at 600 µM. MB was present at a concentration of 30 µM. The error bars indicate data generated from three assays conducted using independent TbHsp70.c, Tbj2, and TcHsp70B protein preparations. Statistical significance was determined by using one-way ANOVA and post-hoc test (* p < 0.01; ** p < 0.001).