Table 1.
Alkaline phosphatases expressed in humans and mice with their basic attributes.
| Isoenzyme AP | Gene | Molecular weight | Tissue localization | Temperature of inactivation | Specific inhibitors | |
|---|---|---|---|---|---|---|
| PLAP | ALPP | 90–120 kDa | Syncytiotrophoblast | Stable at 70°C | neuraminidase [5], L-phenylalanine [58], L-leucine [60], L-leucyl-glycyl-glycine [56], L-phenylalanyl-glycyl-glycine [56] | |
| GCAP | ALPPL2 | PGC, testes, cervix, thymus | ||||
| EAP (mouse) | Akp5 (Alppl2) | Preimplantation stage of embryo | ||||
|
| ||||||
| IAP IAP-like (mouse) |
ALPI (human) Akp3 (mouse) Akp6 (Alpi) |
70–90 kDa | Small intestine (duodenum) | Stable at 56°C | L-Phenylalanine [58], L-tryptophan [59] | |
|
| ||||||
| Bone isoform TNAP |
ALPL (human) Alpl (mouse) |
120–150 kDa | Bone (preosteoblastic cells, basolateral site of osteoblasts), chondrocytes, odontoblasts | PGC (mouse), brain (subependymal layer), embryo, testes (mouse) | Nonstable at 55°C | L-Homoarginine [61], neuraminidase [5], L-levamisole [57], imidazole [62] |
| Liver isoform TNAP | Liver (bille epithelium) | At 55°C more stable than bone isoform | ||||
| Kidney isoform TNAP | Kidney (epithelial cells of proximal tubules) | Nonstable at 45°C | ||||
PLAP: placental AP; GCAP: germ cell AP; EAP: embryonic AP; IAP: intestinal AP; TNAP: tissue nonspecific AP.