Recognition of 2 '-deoxy-L-ribonucleoside 5 '-triphosphates by human telomerase

Telomerase is classified as one of the reverse transcriptases (RTs). To cla rify whether L-enantiomers of natural 2'-deoxyribonucleoside 5'-triphosphat es (cNTPs) are recognized by human telomerase, a quantitative telomerase as say based on the "stretch PCR" method was developed and used for kinetic an alysis of the inhibitory effects of these compounds on the enzyme. Among th e four L-enantiomers of cNTPs, L-dTTP and L-dGTP inhibited telomerase activ ity and the others showed slight or no inhibitory effect. Lineweaver-Burk p lot analysis showed that the inhibition modes of L-dTTP and L-dGTP mere par tially competitive (mixed type) and competitive with the corresponding subs trate dNTP, respectively. However, the K-i values of L-dTTP and L-dGTP (21 and 15 muM) were several times larger than the K-m values (3-6 muM). These results suggest that the active site of telomerase is not able to discrimin ate strictly the chirality of dNTPs, although it is more discriminatory tha n HIV-1 RT. (C) 2000 Academic Press.