Alkaline Phosphatase in Stem Cells

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.