Thermostable Taq DNA Ligase catalyzes the formation of a phosphodiester bond between adjacent 5′-phosphoryl and 3′-hydroxyl cohesive termini in duplex DNA fragments. Catalyzes the formation of a phosphodiester bond between duplex DNA fragments with cohesive ends. Condensation of the 5′-phosphoryl group with an adjacent 3′-hydroxyl group is coupled with the hydrolysis of NAD+. Stable at elevated temperatures (45°C-65°C) allowing enhanced hybridization stringenc. Enzyme suitable for allel-specific gene detection using Ligase Detection Reaction and Ligase Chain Reaction and suitable for mutagenesis by incoporation of a phosphorylated oligonucleotide during PCR amplification.