PPM1B

PPM1B, or protein phosphatase Mg2+/Mn2+-dependent 1B, is a human gene encoding a serine/threonine protein phosphatase that belongs to the protein phosphatase 2C (PP2C) family. As with other PP2Cs, PPM1B is a metal-dependent enzyme that uses divalent cations, typically magnesium or manganese, to catalyze the dephosphorylation of serine or threonine residues on target proteins. The enzyme is generally found in the cytoplasm and can localize to the nucleus under certain conditions, and its expression is widely detected across tissues.

Structure and mechanism: PPM1B contains the conserved catalytic PP2C domain characteristic of the family. It most commonly functions as a monomer, though interactions with other proteins may influence its activity. Its catalytic activity relies on coordination of metal ions, and it is distinguished from many PPP family phosphatases by its distinct catalytic mechanism and inhibitor sensitivities.

Biological role: PPM1B participates in the negative regulation of cellular signaling pathways that are activated by stress. In various cell types, it has been implicated in turning off signaling cascades such as components of the MAP kinase pathways, including p38 and JNK, thereby modulating cellular responses to stress. Through dephosphorylation of select substrates, PPM1B can influence processes such as cell cycle progression, apoptosis, and differentiation.

Clinical and research context: Alterations in PPM1B expression or activity have been investigated in relation to cancer biology and neurological processes, with ongoing research aimed at clarifying its role in disease-relevant signaling networks. PPM1B is one of several PP2C family phosphatases that collectively help shape cellular responses to environmental and intracellular cues.