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Top : Molecular Biology : Enzymatic Manipulation of Nucleic Acid : Alkaline Phosphatase
Overview: Alkaline phosphatases (AP) catalyze the removal of 5' phosphate groups from DNA, RNA, ribo- and deoxyribonucleoside triphosphates. Also they can remove phosphate groups from proteins. These enzymes are most active at alkaline pH - hence the name. There are several sources of alkaline phosphatase that differ in how easily they can be inactivated, such as bacterial alkaline phosphatase (BAP), calf intestinal alkaline phosphatase (CIP) and shrimp alkaline phosphatase. CIP is the most widely used AP and can be effectively destroyed by heat. There are two main applications for alkaline phosphatase in nucleic acid manipulations: 1)Removing 5' phosphates from plasmid and bacteriophage vectors that have been cut with a restriction enzyme. In subsequent ligation reactions, this treatment prevents self-ligation of the vector and thereby greatly facilitates ligation of other DNA fragments into the vector; 2) Removing 5' phosphates from DNA fragments prior to labeling with radioactive phosphate.
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