Tobacco acid pyrophosphatase explained

Tobacco Acid Pyrophosphatase (TAP) is an enzyme that catalyses the hydrolysis of a phosphoric ester bond in a broad spectrum of molecules,^[1] including the 5'-end of mRNA.

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.^[2] 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,^[3] 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.^[4]

Notes and References

1. Shinshi H, Miwa M, Kato K, Noguchi M, Matsushima T, Sugimura T . 1976 . A novel phosphodiesterase from cultured tobacco cells. Biochemistry . 15. 10 . 2185–90 . 6041. 10.1021/bi00655a024.
2. Book: JEREMY M. BERG . JOHN L. TYMOCZKOL . LUBERT STRYER . 2002 . Biochemistry. registration . 28.3.1. Online version
3. Lockard, RE . Rieser, L . Vournakis JN. . 1981 . Labeling of eukaryotic messenger RNA 5' terminus with phosphorus -32: use of tobacco acid pyrophosphatase for removal of cap structures. Gene Amplif Anal . 2. 229–51. 6152889 .
4. Pelechano . Vicent . Wei . Wu . Steinmetz . Lars M. . February 2016 . Genome-wide quantification of 5′-phosphorylated mRNA degradation intermediates for analysis of ribosome dynamics . Nature Protocols . en . 11 . 2 . 359–376 . 10.1038/nprot.2016.026 . 26820793 . 4732566 . 1750-2799.