SBPase, or sedoheptulose-bisphosphatase, is an enzyme that removes a phosphate from sedoheptulose 1,7-bisphosphate to produce sedoheptulose 7-phosphate and phosphate. It is a homodimeric protein with a mass of about 92 kDa (or 46 kDa for each subunit). SBPase requires a magnesium cofactor and the formation of a cysteine disulfide bond for activity. SBPase plays a role in the Calvin cycle.