The enzyme inositol-polyphosphate 5-phosphatase (), systematic name 1<small>D</small>-myo-inositol-1,4,5-trisphosphate 5-phosphohydrolase, catalyses the following reactions:
Ten mammalian isoforms are known.
Other names of this enzyme include type I inositol-polyphosphate phosphatase, inositol trisphosphate phosphomonoesterase, InsP<sub>3</sub>/Ins(1,3,4,5)P<sub>4</sub> 5-phosphatase, inosine triphosphatase, <small>D</small>-myo-inositol 1,4,5-triphosphate 5-phosphatase, <small>D</small>-myo-inositol 1,4,5-trisphosphate 5-phosphatase, <small>L</small>-myo-inositol 1,4,5-trisphosphate-monoesterase, inositol phosphate 5-phosphomonoesterase, inositol-1,4,5-trisphosphate/1,3,4,5-tetrakisphosphate 5-phosphatase, Ins(1,4,5)P<sub>3</sub> 5-phosphatase<small>D</small>-myo-inositol(1,4,5)/(1,3,4,5)-polyphosphate 5-phosphatase, inositol 1,4,5-trisphosphate phosphatase, inositol polyphosphate-5-phosphatase, myo-inositol-1,4,5-trisphosphate 5-phosphatase, inositol-1,4,5-trisphosphate 5-phosphatase.