Figure 2. Esterase-like activity measured in human saliva, collected from different subjects and measured with para-nitrophenylacetate (p-NPA), ortho-nitrophenylacetate (o-NPA), para-nitrophenylbutyrate (p-NPB), and ortho-nitrophenylbutyrate (o-NPB), (pH 7.0 at 25°C).