title: Substrate specificity of nuclease TT1 from Thermus thermophilus HB8.
abstract: The substrate and the action mechanism of a nuclease named nuclease TT1, from the culture broth of an extreme thermophile, Thermus thermophilus HB8, were investigated. The enzyme is nonspecific for the sugar moiety and cleaves both single- and double-stranded DNAs, rRNA, tRNA and oligonucleotides irrespective of chain length to produce 5'-mononucleotides exonucleolitically. The action mechanism is processive and the enzyme shows no porality of degradation. The minimal unit as a substrate is a 5'-dinucleotide. The rate of hydrolysis is independent of a terminal phosphate group. The substrate lacking a 5'-phosphoryl group is degraded to leave the 5'-terminus and the penultimate nucleotide (NpN) as a core. The substrate possessing a 3'-phosphoryl group is degraded to leave the mononucleoside 5',3'-diphosphates (pNp). However, NpN and pNp are gradually degraded by a large dose of the enzyme to produce a 5'-mononucleotide. The enzyme is free from nonspecific phosphatase and phosphodiesterase activities. Application of this enzyme to determine the sequence of oligonucleotides is shown.
mesh_terms: D005092:Exonucleases / Q000378:metabolism*; D007700:Kinetics; D011089:Polydeoxyribonucleotides; D011131:Polyribonucleotides; D013379:Substrate Specificity; D013824:Thermus / Q000201:enzymology*
chemical_list: D011089:Polydeoxyribonucleotides; D011131:Polyribonucleotides; D005092:Exonucleases; C025422:nuclease TT1