| abstract |
The key function of TNAP in bone is degradation of PPi to remove this mineralization inhibitor and provide free phosphate for apatite deposition. PC-1 is a direct antagonist of TNAP function. ANK also antagonizes TNAP-dependent matrix calcification. Specifically, the activity of PC-1 inhibits initial MV apatite deposition, but ANK inhibits propagation of apatite outside the MVs. Furthermore, loss of function of the two distinct skeletal TNAP antagonists, PC-1 and ANK, ameliorates TNAP deficiency-associated osteomalacia in vivo. Conversely, the hyperossification associated with both PC-1 null mice and ANK-deficient (ank/ank) mice is ameliorated by deficiency of TNAP in vivo. |