Protein phosphatase (PPase) inhibition assay (PPIA) is widely
used to analyze the concentration of microcystins (MCs) because
it is comparatively less expensive and faster than other
assays. This study aimed to optimize the PPIA by determining
a suitable reaction terminator and an optimal methanol
concentration in the sample. The most suitable reaction time
was 90 min, with the corresponding methanol concentration
in the sample being 15% or less. When p-nitrophenyl phosphate
(pNPP) was used as a substrate, copper chloride solution
was suitably used as a reaction terminator, and when 4-
methylumbelliferyl phosphate (MUP) was used, a glycine buffer
not only increased the measurement sensitivity of the reaction
product but also terminated the enzymatic reaction.
When PPase 1 and MUP were used as an enzyme and a substrate,
respectively, the limit of quantitation for MC-leucine/
arginine (LR) was 0.02 μg/L, whereas it was 0.1 μg/L when
pNPP was used as a substrate. The proposed method facilitated
the measurement of MC-LR concentration without
additional pretreatments, such as concentration or purification;
therefore, this method was suitable and feasible for the
continuous monitoring of MCs in drinking water.
Citations
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