Protein Phosphatase Specificity Chart

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  • NEB offers protein phosphatases with varied specificities towards tyrosine, serine and threonine residues.

    Phosphatase Specific Activity (nmol/min/mg) Units Required or 100% Phosphate Removal NEB #
    PSP PTP PNPP
    TC PTP 0 2,400 48,250 1-5 P0752
    Lambda PP 26,600 2,200 1,290,000 100–500 P0753
    PP1 14,100 1,860 58,600 0.1–1 P0754
    Alkaline Phosphatase, CIP 1,520 26,440 128,300 10–50 M0290
    Antarctic Phosphatase 750 720 7,880 1–5 M0289

    Specific protein phosphatase activities were determined using myelin basic protein (MyBP) from bovine brain. Serine and threonine residues were labeled using cAMP-dependent protein kinase (PKA) (1) in the presence of [33P] ATP, yielding incorporation of 2-4 mol phosphates per mol MyBP. Tyrosine residues were similarly labeled using Abl protein tyrosine kinase (2), yielding incorporation of 1-2 mol phosphate per mol MyBP. The amount of incorporated 33P was determined by separation of phosphorylated MyBP from [33P] ATP using TCA precipitation technique and the quantitation of radioactively labelled protein (3).

    The protein phosphatase activities (PSP and PTP) were determined by measuring the release of inorganic phosphate (TCA-soluble 33P-radioactivity) from labeled MyBP (3).

    PNPP phosphatase activity was determined spectrophotometrically by following hydrolysis of a non-proteinaceous substrate PNPP (3).

    Specific protein and PNPP phosphatase activities were determined under standard conditions, which can be found on the product data card for each enzyme. All phosphatases were incubated with 10 μM phospho-MyBP (concentration of incorporated phosphate) or with 50 mM PNPP in a 50 μl reaction for 10 minutes to ensure the linear range of dephosphorylation.

    References:

    1. Slice, L.W. and Taylor, S.S. (1989) J. Biol. Chem. 264, 20940–20946. PMID: 2687267 
    2. Foulkes, J.G. et al. (1985) J. Biol. Chem. 260, 8070-8077. PMID: 2989275 
    3. MacKintosh, C. (1993). In D.G. Hardie (Ed.), Protein Phosphorylation: A Practical Approach. New York: IRL Press.