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Fluorescein monophosphates as fluorogenic substrates for protein tyrosine phosphatases
Q Wang1, J Scheigetz, M Gilbert
1Department of Biochemistry and Molecular Biology, Merck-Frosst Center for Therapeutic Research, P.O. Box 1005, Pointe-Claire-Dorval, Que. H9R 4P8, Canada. qingping_wang@merck.com
Biochimica Et Biophysica Acta
|April 21, 1999
Summary
New fluorescein monophosphate substrates offer a simpler, more sensitive method for studying protein tyrosine phosphatases (PTPs). These novel compounds, unlike fluorescein diphosphate (FDP), are dephosphorylated in a single step, improving assay accuracy.
Area of Science:
- Biochemistry
- Enzymology
- Fluorescent Probes
Background:
- Protein tyrosine phosphatases (PTPs) are crucial enzymes involved in cell signaling.
- Existing fluorescent substrates like fluorescein diphosphate (FDP) present assay complications due to sequential dephosphorylation.
- There is a need for improved substrates for accurate PTP activity measurement.
Purpose of the Study:
- To synthesize and evaluate novel fluorescein monophosphate derivatives as substrates for PTPs.
- To compare the performance of these new substrates against FDP.
- To identify a superior fluorescent substrate for PTP assays.
Main Methods:
- Chemical synthesis of novel fluorescein monophosphate analogs.
- Enzymatic assays using various PTPs (e.g., CD45, PTP1B).
- Kinetic analysis to determine Michaelis-Menten parameters (Km, kcat/Km).
Main Results:
- Novel monophosphates undergo single-step dephosphorylation, simplifying PTP assays.
- Substrates exhibited Michaelis-Menten parameters in the range of Km 0.03-0.35 mM and kcat/Km 3-100 mM⁻¹s⁻¹.
- Fluorescein monosulfate monophosphate (FMSP) demonstrated high affinity and sensitivity, with significant fluorescence increase upon dephosphorylation at pH > 6.0.
Conclusions:
- Novel fluorescein monophosphates are effective substrates for PTPs, overcoming limitations of FDP.
- FMSP is identified as a highly sensitive, stable, and high-affinity substrate for PTPs.
- These findings facilitate more accurate and efficient studies of PTP activity and function.