A phosphatase is an enzymethathydrolysesphosphoric acidmonoestersinto aphosphateionand a molecule with a free hydroxylgroup. This action is directly opposite to that of phosphorylasesandkinases, which attach phosphate groups to their substrates by using energetic molecules like ATP. A common phosphatase in the body is alkaline phosphatase.

The presence or absence of the phosphategroup on proteins, especially enzymes, is known to play a regulatory role in many biochemical pathwaysand signal transductionpathways. Hence together, specialized kinases and phosphatases regulate enzymatic activity.

Phosphatases can be categorised into two main categories: metalloenzymes(which are dependent on the presence of two or more metal ions in their active sites for activity), and non- metalloenzymes. These categories can then be divided into further sub-categories.

Best known of the non-metalloenzymes are the protein tyrosine phosphatases, which hydrolyse phospho- tyrosine residues. However, the metalloenzymes by far comprise the greatest bulk of phosphatases, and contain such enzymes as alkaline phosphatase(three metal ions, only two of which are catalytically active), the serine threonine phosphatases and inositol monophosphatase (a key enzyme in manic depression).

(source: Wikipedia)

AnaSpec		Protein Phosphatase Assay Kits
invitrogen		Phosphatases
		Phosphatase Substrates
Innova biosciences		Universal assay regaentsfor phosphatasesand nucleotidases.
Biotium		alkaline phosphatase substrates