title: DNA nicking--closing activity from salmon testis.
abstract: Salmon testis is a good source of DNA nicking--closing (N--C) enzyme, as expected for rapidly proliferating cells. Partial purification was obtained but it resulted in an unstable form of N--C enzyme. Cruder fractions are useful for relaxing supercoiled DNA under conditions where other N--C enzymes are inactive. The enzyme is very tolerant of salt concentration, with activity still detectable at 0.6 M NaCl. It is also active at low temperatures with reasonable activity at 0 degrees C. However, at temperatures greater than 25 degrees C it is rapidly inactivated. Otherwise, its properties are similar to other eucaryotic N--C enzymes.
mesh_terms: D000818:Animals; D004264:DNA Topoisomerases, Type I / Q000302:isolation & purification / Q000378:metabolism*; D008297:Male; D012474:Salmon; D013737:Testis / Q000201:enzymology*
chemical_list: D004264:DNA Topoisomerases, Type I