Serine/threonine-protein phosphatase 2A regulatory subunit B<nowiki></nowiki> subunit beta is an enzyme that in humans is encoded by the PPP2R3B gene.
Protein phosphatase 2 (formerly named type 2A) is one of the four major Ser/Thr phosphatases and is implicated in the negative control of cell growth and division. Protein phosphatase 2 holoenzymes are heterotrimeric proteins composed of a structural subunit A, a catalytic subunit C, and a regulatory subunit B. The regulatory subunit is encoded by a diverse set of genes that have been grouped into the B/PR55, B'/PR61, and B<nowiki></nowiki>/PR72 families. These different regulatory subunits confer distinct enzymatic specificities and intracellular localizations to the holozenzyme. The product of this gene belongs to the B<nowiki></nowiki> family. The B<nowiki></nowiki> family has been further divided into subfamilies. The product of this gene belongs to the beta subfamily of regulatory subunit B<nowiki></nowiki>. Alternative splicing results in multiple transcript variants encoding different isoforms.
PPP2R3B has been shown to interact with PPP2R1B, PPP2R1A, CDC6 and PPP2CA.