Membrane-bound transcription factor peptidase site 2 also known as Site-2 Protease (S2P) is an enzyme (EC 3.4.24.85) encoded by the MBTPS2 gene which liberates the N-terminal fragment of sterol regulatory element binding protein (SREBP) transcription factors from membranes. S2P cleaves the transmembrane domain of SREPB making it a member of the class of intramembrane proteases.