Magnesium-dependent phosphomonoesterase

Magnesium-dependent phosphomonoesterases are a diverse group of enzymes that utilize magnesium ions (Mg2+) as essential cofactors to catalyze the hydrolysis of phosphate monoesters [2, 13]. This family includes critical metabolic and signaling enzymes such as inositol monophosphatase (IMPase), inositol polyphosphate 1-phosphatase (INPP1), and fructose-1,6-bisphosphatase (FBPase) [2, 6]. These enzymes are the primary molecular targets of lithium, a mainstay treatment for bipolar disorder; lithium acts as an uncompetitive inhibitor by displacing magnesium from the active site, thereby disrupting the phosphoinositide cycle and reducing intracellular inositol levels [1, 2, 3]. Beyond psychiatry, certain members like the protein phosphatase magnesium-dependent 1 delta (PPM1D) are involved in the DNA damage response and are frequently overexpressed in various cancers, making them attractive targets for oncology drug development [8, 10]. The therapeutic modulation of these enzymes requires careful management due to their broad physiological roles and the narrow therapeutic index of existing inhibitors like lithium [4].

Other names

Lithium-sensitive phosphomonoesterasesMg2+-dependent phosphatasesInositol monophosphatase familyPhosphoric monoester hydrolases (magnesium-dependent)

Uncompetitive inhibition by lithium ions, which compete with magnesium ions for binding sites in the enzyme-substrate complex, preventing the release of phosphate and recycling of inositol [2, 3]. This leads to the depletion of intracellular inositol, dampening overactive signaling pathways [3, 6].