Research Article

The Role of Arg13 in Protein Phosphatase M tPphA from Thermosynechococcus elongatus

Table 2

Kinetic parameters of tPphA and Arg-13 variants towards pNPP. pNPP assays were carried out as described in Experimental Procedures (Subsection 2.2). The pH of the reaction was 8.3. From the apparent reaction velocities of three independent repetitions, the kinetic parameters were calculated by linear fitting using the program GraphPad Prism 4. ± indicates standard error. The results were obtained from single preparations of the wild-type (WT) and variant tPphA purifications.

Classification of Arg-13 variantsVariants [mM] (pNPP) [s−1] pNPP / [s-1 M−1]

Arg-13 changed to residues with electrically charged side chainsWT(R13R)
R13K
R13H
R13D

Arg-13 changed to residues with polar uncharged side chainsR13S
R13T
R13N
R13Q

Arg-13 changed to residues with hydrophobic side chainsR13A
R13L
R13I
R13M

Arg-13 changed to residues with aromatic side chainsR13F
R13W
R13Y

Arg-13 changed to residues with special side chainsR13G
R13C
R13P

—: not detectable.