Inositol Polyphosphate-4-Phosphatase Type II 105kDa (INPP4B)

INPP4B encodes the inositol polyphosphate 4-phosphatase type II, one of the enzymes involved in phosphatidylinositol signaling pathways. This enzyme removes the phosphate group at position 4 of the inositol ring from inositol 3,4-bisphosphate. There is limited data to suggest that the human type II enzyme is subject to alternative splicing, as has been established for the type I enzyme. Unlike INPP4A, INPP4B does not have a PEST sequence. The human and rat proteins share 90% sequence identity. Northern blot analysis revealed ubiquitous expression, with primary transcripts of 9.5, 5.3, 3.9, and 2.9 kb. Highest expression was detected in skeletal muscle and heart, with intermediate levels in brain, placenta, and pancreas, and lowest levels in liver, kidney, and lung. The 5.3-kb transcript was detected only in brain.