Figure 4.

PfA-M17 and Pv-M17 hydrolyze the cysteinyl-glycine dipeptide. Activity of, A, PfA-M17 and, B, Pv-M17 against cysteinyl-glycine dipeptide in the presence of 0.2 mM Zn²⁺, Mn²⁺, Co²⁺, Mg²⁺, and with no metal ions added in buffer varying pH from 6.0 to 9.0. Amount of liberated cysteine was detected using ninhydrin and the resultant absorbance measured at 560 nm. Both PfA-M17 and Pv-M17 are only active against the dipeptide in the presence of Mn²⁺, PfA-M17 at pH 8.0, and Pv-M17 at pH 7.0 and pH 8.0.