Methods in Molecular Biology • 16 Enzymes of Molecular Biology

CHAPTER 19

Alkaline Phosphatase (EC 3.1.3.1)

Martin J. Maunders

1. Introduction
   Alkaline phosphatases (or alkaline phosphomonoesterases) cata-
   lyze the hydrolysis of phosphate monoesters of a variety of alcohol
   moieties, being most active at an alkaline pH. The enzymes have been
   isolated from a variety of sources, including bacteria, fungi, inverte-
   brates, fish, and mammals (being located in many organs, including
   bone marrow, kidney, placenta, and intestinal mucosa), but have not
   been isolated from higher plants. The most commonly used alkaline
   phosphatases (AP) are those from calf intestinal mucosa (called CIAP,
   CIP, or CAP) and from the bacterium Escherichia coli (BAP).
   The in vivo function of the enzyme is unclear, since its phosphatase
   activity is nonspecific. In bone tissue, it may be involved in ossifica-
   tion by formation of calcium phosphate (1), whereas in other mamma-
   lian tissues, a role in phosphate transport has been suggested.
   The bacterial enzyme is expressed constitutively in most species, an
   exception being E. coli, where synthesis is repressed by orthophos-
   phate (2). On phosphate starvation, BAP is secreted into the periplasmic
   lumen (3). Again a role has been suggested in a phosphate transport
   system (4).
   The enzyme has two common uses in molecular biology. First, it is
   used as a reporter in detection systems for particular protein or nucleic
   acid molecules, and second, to dephosphorylate the termini of nucleic
   acids enabling subsequent in vitro modification.

From: Methods in Molecular Biology, Vol. 16: Enzymes of Molecular Biology

Edited by: M. M. Burrell Copyright ©1993 Humana Press Inc., Totowa, NJ

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