Active at a high pH optimum. Wide specificity. Also catalyzes transphosphorylations. Some enzymes hydrolase diphosphate.

Alkaline phosphatase is a zinc and magnesium-containing metalloenzyme which hydrolyzes phosphate esters, optimally at high pH. It is found in nearly all living organisms, with the exception of some plants. In Escherichia coli, ALP is found in the periplasmic space. In yeast it is found in lysosome-like vacuoles and in mammals, it is a glycoprotein attached to the membrane by a GPI-anchor.

In mammals, four different isozymes are currently known. Three of them are tissue-specific: the placental, placental-like (germ cell) and intestinal isozymes. The fourth form is tissue non-specific and was previously known as the liver/bone/kidney isozyme.

A serine is involved in the catalytic activity of ALP. The region around the active site serine is relatively well conserved and can be used as a signature pattern.
Reference