TdT -Terminal deoxynucleotidyl transferase.
Terminal deoxyribonucleotidyl transferase (EC catalyzes the repetitive addition of mononucleotides from deoxynucleoside triphosphates to the terminal 3´-OH of a DNA initiator. ssDNA is preferred as an initiator. However, blunt or recessed 3´ termini are used, albeit less efficiently, in buffers of low ionic strength that contain Co2+, Mg2+, or Mn2+. Will accept ddNTPs, succinylfluorescein-ddNTPs, rNTPs, biotin-11-dUTP, cordycepin triphosphate and phosphorothioate deoxynucleotide (dNTPaS) for terminal addition. Single nucleotides can be added to the 3´ termini of DNA if modified nucleotides (rNTPs, ddNTPs, cordycepin triphosphate) are used as substrate.
Unit definition

1 unit catalyzes the transfer of 1 nmol of dATP to poly(dT)50 in 1 h at 37°C.

Reaction buffer
#B33 (x5): 500 mM Na cacodidylate pH 7.2, 1 mM 2-mercaptoethanol, 10 mM CoCl2.
Reaction conditions
Store at -20°C.
cloning; labeling of the 3´-hydroxyl ends of single- and double-stranded DNA, introduction of mispaired primer ends for site-directed mutagenesis protocols; apoptosis TUNEL assay; as a marker in leukemia diagnosis.

Quality control

activity, SDS-PAGE purity, absence of endonuclease/nickase, RNase and DNase activities, specific performance tests.


1. Bollum, F.J. (1974) in The Enzymes (Boyer, P.D., ed.) Academic Press, NY, 145-171. 2. Deng, G., Wu, R. (1983) Methods Enzymol. 100, 96-116.

Catalog #





Pack size

500 U

1.000 U





Copyright © 2002 M.B. Enzymes GmbH