Thermus Aquaticus - Enzymes From T. Aquaticus

Enzymes From T. Aquaticus

T. aquaticus has become famous as a source of thermostable enzymes, particularly the "Taq" DNA polymerase, as described below.

Aldolase

Studies of this extreme thermophilic bacterium that could be grown in cell culture was initially centered on attempts to understand how protein enzymes (which normally inactivate at high temperature) can function at high temperature in thermophiles. In 1970, Freeze and Brock published an article describing a thermostable aldolase enzyme from T. aquaticus.

RNA polymerase

The first polymerase enzyme isolated from T. aquaticus in 1974, was a DNA-dependent RNA polymerase, used in the process of transcription.

Taq I restriction enzyme

For more details on this topic, see TaqI.

Most molecular biologists probably became aware of T. aquaticus in the late 1970s or early 1980s because of the isolation of useful restriction endonucleases from this organism. Use of the term "Taq" to refer to Thermus aquaticus arose at this time from the convention of giving restriction enzymes short names, such as Sal and Hin, derived from the genus and species of the source organisms.

DNA polymerase ("Taq pol")

For more details on this topic, see Taq polymerase.

DNA polymerase was first isolated from T. aquaticus in 1976. The first advantage found for this thermostable (temperature optimum 80°C) DNA polymerase was that it could be isolated in a purer form (free of other enzyme contaminants) than could the DNA polymerase from other sources. Later, Kary Mullis and other investigators at Cetus Corporation discovered this enzyme could be used in the polymerase chain reaction (PCR) process for amplifying short segments of DNA, eliminating the need to add enzyme after every cycle of thermal denaturation of the DNA. The enzyme was also cloned, sequenced, modified (to produce the shorter 'Stoffel fragment'), and produced in large quantities for commercial sale. In 1989 Science magazine named Taq polymerase as its first "Molecule of the Year". In 1993, Dr. Mullis was awarded the Nobel Prize for his work with PCR.

Other enzymes

The high optimum temperature for T. aquaticus allows researchers to study reactions under conditions for which other enzymes lose activity. Other enzymes isolated from this organism include DNA ligase, alkaline phosphatase, NADH oxidase, isocitrate dehydrogenase, amylomaltase, and fructose 1,6-disphosphate-dependent L-lactate dehydrogenase.