Protein phosphatase type 2C active at physiological Mg2+: stimulation by unsaturated fatty acids

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Type 2C serine/threonine protein phosphatases (PP2C) typically require high Mg2+ concentrations for activity.
• The regulation and specific activators/inhibitors of PP2C isozymes remain largely unknown.
• Previous studies may have underestimated PP2C activity due to non-physiological assay conditions.

Purpose of the Study:

• To investigate novel activators and regulatory mechanisms for PP2C isozymes.
• To explore the role of fatty acids in modulating PP2C activity.
• To differentiate the enzymatic properties of PP2C isozymes.

Main Methods:

• Enzyme activity assays using bovine retinal PP2C isozymes (PP2Calpha and PP2Cbeta).
• Testing the effects of various concentrations of mono- and polyunsaturated fatty acids (e.g., arachidonic acid) on PP2C activity.
• Investigating the influence of different Mg2+ and Ca2+ ion concentrations on enzyme kinetics.

Main Results:

• Mono- and polyunsaturated fatty acids significantly activated PP2C isozymes, particularly at low Mg2+ concentrations.
• Arachidonic acid demonstrated a 10-fold stimulation of PP2Calpha activity at 0.7 mM Mg2+.
• PP2Cbeta exhibited 30-50% less sensitivity to fatty acid activation compared to PP2Calpha, highlighting isozyme-specific differences.
• Fatty acid-mediated activation resulted in significantly higher dephosphorylation rates than previously observed.
• Ca2+ ions exhibited inhibitory effects in the micromolar range in the presence of fatty acids.

Conclusions:

• Unsaturated fatty acids are potent activators of PP2C enzymes.
• These findings suggest a crucial physiological role for unsaturated fatty acids in PP2C regulation.
• PP2C activity has likely been underestimated in prior research due to the absence of these activators.
• Isozyme-specific differences in PP2C regulation by fatty acids were identified.