Overview:

• Isolated from the thermophilic bacterium Thermus aquaticus
• Thermostable DNA polymerase
• Catalyzes 5’→3′ DNA synthesis (5’→3′ polymerase activity) from primed single-stranded DNA in the presence of Mg2+
• Possesses low 5’→3′ exonuclease activity
• Lacks 3′→5′ exonuclease activity (proofreading)
• Exhibits deoxynucleotidyl transferase activity (addition of extra adenines at the 3′-end of PCR products)
• Error rate: 1 × 10–5 errors/base
• Extension rate: >60 nucleotides/second at 70°C (Innis et al., 1988)
• Half life at 95°C: 40 minutes

Applications

• Frequently used for polymerase chain reaction, suitable for PCR reactions that do not require high-fidelity enzymes, frequently used for the amplification of upto 5 kb DNA fragment
• DNA labeling (Oligo probe preparation)

Description

• Taq DNA polymerase is a thermostable DNA-dependent DNA polymerase originally isolated from the thermophilic bacterium Thermus aquaticus, which thrives in hot environments such as hydrothermal vents and hot springs. 
• The enzyme is renowned for its ability to synthesize DNA at high temperatures, making it an indispensable tool in molecular biology—particularly in the polymerase chain reaction (PCR).
• Taq polymerase catalyzes the 5′→3′ polymerization of deoxyribonucleotides into a DNA strand, using a DNA template and primer. Its optimum temperature for activity is around 72–75°C, which aligns well with the elongation phase of PCR. Because it remains stable at the high denaturation temperatures (~94–95°C) used in PCR cycles, it eliminates the need to replenish polymerase after each cycle, which was a major limitation before thermostable enzymes were discovered.
• While Taq polymerase is highly efficient and fast—adding approximately 1,000 bases per minute—it lacks 3′→5′ exonuclease (proofreading) activity, which means it does not correct mistakes during DNA synthesis. As a result, it has a relatively high error rate (~1 in 10⁴–10⁵ bases), which is acceptable for many standard applications but less ideal for high-fidelity cloning or sequencing purposes. For such needs, high-fidelity polymerases with proofreading abilities (like Pfu or Q5) are preferred.
• Despite this limitation, Taq polymerase remains a workhorse enzyme in PCR-based applications such as genotyping, cloning, mutagenesis, diagnostic testing, and forensic DNA analysis. It is typically supplied as a recombinant protein and often formulated with buffers and stabilizers for enhanced performance across diverse protocols.
• In summary, Taq polymerase revolutionized molecular biology by enabling automated, high-temperature DNA amplification, and continues to be a fundamental component in nucleic acid research, diagnostics, and biotechnology.

REFERENCES:

• Innis et al., 1988. DNA sequencing with Thermus aquaticus DNA polymerase and direct sequencing of polymerase chain reaction-amplified DNA. Proc Natl Acad Sci U S A. 85(24), 9436-9440. PMID-3200828; Full Text Links: pnas (download PDF), PMC282767
• Lawyer et al., 1993. High-level expression, purification, and enzymatic characterization of full-length Thermus aquaticus DNA polymerase and a truncated form deficient in 5′ to 3′ exonuclease activity. PCR Methods Appl. 2(4), 275-287. PMID-8324500; Full Text Link: cshlp (download PDF)