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. Author manuscript; available in PMC: 2010 May 19.
Published in final edited form as: Biochemistry. 2009 May 19;48(19):4086–4099. doi: 10.1021/bi802059r

Figure 2.

Figure 2

Spectroscopic assay on determination of the optimal conditions for the PfPM1 catalysis. (a) The proPfPM1 K110pN mutant was incubated at 37 °C in 0.1 M sodium formate pH 3.5, 0.1 M sodium formate pH 4.0 and 0.1 M sodium acetate pH 4.5. The hydrolyses of the activated PfPM1 on 100 µM of chromogenic peptide substrate A were monitored at a variety of time points from 0 to 4 h, and the corresponding initial cleavage velocities were measured and normalized. The zymogen can be efficiently activated and performs catalysis at pH 4.0 and 4.5. The optimal condition for the catalysis of PfPM1 is at pH 4.5 with 20 min preincubation. (b) The mature PfPM1 was incubated at 37 °C for 3 min in a series of acidic buffers from pH 3.5–6.0. The initial cleavage velocities of mature PfPM1 on 100 µM of chromogenic peptide substrate A were measured and normalized. The optimal pH for mature PfPM1 to perform catalysis was pH 5.5. All the assays were repeated three times, from which the average and standard errors were calculated.