发信人: space (排骨教主), 信区: Biology
标 题: Topoisomerases
发信站: The unknown SPACE (Wed Feb 23 01:00:30 2000), 站内信件

DNA topoisomerases are enzymes that catalyze the passage of individual DNA
strands or double helices through one another. These reactions are often
manifested in interconversions between topological isomers of DNA rings;
hence the name of the enzymes...

There are three enzymes in this group: E.coli DNA topoisomerase I,
mouse DNA topoisomerase I, and E.coli topoisomerase II, respectively,
representing 3 distinct subfamilies of topoisomerases.

Both E.coli DNA topoisomerase I and mouse DNA topoisomerase I are classified
as type I enzynes, which effect topoloical changes by transiently cleaving
one dna strand at a time to allow the passage of another strand;

E.coli gyrase or DNA topoisomerase II is a member of the type II
topoisomerases. The type II enzyme catalize DNA topological transformation
by transiently cleaving a pair of complementary DNA strands in one duplex
segment to form an enzyme operated gate in the segment. A second double
stranded DNA segment is then passed through the gate by the enzyme, after
which the severed starnds in the first DNA segment are rejoint.

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※ 来源:．The unknown SPACE bbs.mit.edu．[FROM: 131.193.173.223]