Tobacco Acid Pyrophosphatase (TAP) is an
enzyme
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
that catalyses the hydrolysis of a
phosphoric ester
In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distincti ...
bond in a broad spectrum of molecules, including the 5'-end of
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
.
During mRNA maturation the 5' triphosphate of the new mRNA molecule is rapidly removed. The diphosphate 5' end then attacks the α-phosphorus atom of a methylated
GTP to form a very unusual 5'-5' triphosphate linkage, called ''cap''. In molecular biology, TAP is used to hydrolyse a phosphodiester bond of this particular structure and release a mRNA molecule with only one phosphate group in the 5'-end, for instance in protocols for
RACE (Rapid Amplification of cDNA Ends).
Commercial production of TAP was discontinued in 2015, however Cap-Clip acid pyrophosphatase has been found to perform nearly identically in genome-wide studies.
References
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Enzymes