Taq Polymerase 33
Table 1
Inhibitor Effects on Taq Polymerase I Activity ~
Inhibitor Concentration % Activity
Urea <0.5M 100
1.0M 118
1.5M 107
2.0M 82
SDS 0.001% 105
0.01% 10
0.1% <0.1
Ethanol <3 % 100
10% 110
DMSO <1% 100
10% 53
20% 110
DMF <5 % 100
10% 82
20% 17
aBased on results from ref. 7.activity. Denaturating agents, detergents, and organic solvents in low
concentration are tolerated by Taq polymerase; at higher concentra-
tions, inhibition is observed.
A compilation of the effects of several substances is shown in Table 1.
These concentrations are not obligatorily applicable to the PCR; e.g.,
0.5M Urea are inhibitory to the PCR, whereas up to 1.5M Urea do not
alter the incorporation yields of Taq polymerase. The inhibition by
0.01% SDS can be reversed by adding 0.1% Tween 20 or NP40 (7).
Taq polymerase is an enzyme with high processivity (8). An absolute
requirement is a DNA template with a primer to initiate the reaction. The
primer must be dephosphorylated on the 3' end (7). Taq polymerase has
a strand displacement 5'-3' exonuclease activity. 5'-phosphorylated
oligodeoxynucleotides are not degraded by the 5'-3' exonuclease activity
of the enzyme. Studies of the fidelity of DNAsynthesis by Taq polymerase
revealed error rates of 1.1 x 10 -4 for misincorporation and 2.5 x 10 -5 for
frameshift mutations (6). An error rate of 2 × 10-4 was determined by PCR
experiments followed by sequencing (3) and by denaturing gradient gel
electrophoresis (9). T-C transitions are occurring more frequently than
other misincorporation errors (6,10).