TABLE 1 

Substrate specificities of purified His6-PipA and His6-AapA enzymes

SubstrateMean activity ± SDa
His6-PipAHis6-AapA
l-Proline-β-naphthylamide 100.0 ± 13.4 9.7 ± 0.8
l-Alanine-β-naphthylamide 79.4 ± 12.5 331.1 ± 39.9
l-Hydroxy-proline-β-naphthylamide 30.4 ± 1.3 23.5 ± 2.6
l-Serine-β-naphthylamide 21.5 ± 2.6 12.0 ± 0.5
l-Leucine-β-naphthylamide 7.7 ± 1.8 2.1 ± 1.0
l-Histidine-β-naphthylamide ND 2.9 ± 0.8
l-Glutamic acid-β-naphthylamide ND ND
l-Proline-p-nitroanilide 0.72 ± 0.01 0.006 ± 0.001
l-Methionine-p-nitroanilide 0.17 ± 0.02 0.160 ± 0.021
l-Lysine-p-nitroanilide ND ND
  • a Enzyme (PipA [PMI36_04624] and AapA [PMI36_04622]) purification and assay conditions are described in Materials and Methods; the results are the mean activities from 4 to 8 assays. Naphthylamide substrate results were measured as relative fluorescence units (RFU) per min per mg of protein and normalized to the activity exhibited by His6-PipA with L-proline-β-naphthylamide as the substrate. Nitroanilide substrate results are reported as millimoles cleaved per min per mg of protein. ND, not detected (not above the background of the no-added-enzyme control).