Inositol 1,4,5‐trisphosphate activity in membranes isolated from amphibian skeletal muscle

Abstract
The hydrolysis of [3H]inositol 1,4,5‐trisphosphate by a soluble fraction and by isolated transverse tubule and sarcoplasmic reticulum membranes from frog skeletal muscle was studied. Transverse tubule membranes displayed rates of hydrolysis several‐fold higher than those of sarcoplasmic reticulum and soluble fraction; K m and V max were 25.2 μM and 44.1 nmol/mg/min, respectively. Transverse tubule membranes sequentially hydrolyzed inositol trisphosphate to inositol bisphosphate, inositol 1‐phosphate and inositol. Indicating that these membranes have inositol bis‐ and monophosphatases in addition to inositol trisphosphatase.