Method of amplifying circular DNA

A method for amplifying circular DNA, comprising:

• (1) providing a reaction mixture of circular DNA as a template with a reaction solution comprising:
• a first enzyme group that catalyzes replication of circular DNA, wherein the first enzyme group comprises an enzyme having DnaA activity, one or more types of a nucleoid protein, an enzyme or enzyme group having DNA gyrase activity, single-strand binding protein (SSB), an enzyme having DnaB-type helicase activity, an enzyme having DNA helicase loader activity, an enzyme having DNA primase activity, an enzyme having DNA clamp activity, and an enzyme or enzyme group having E. coli DNA Polymerase III* activity;
• a second enzyme group that catalyzes an Okazaki fragment maturation and synthesizes two sister circular DNAs constituting a catenane, wherein the second enzyme group comprises an enzyme having E. coli DNA Polymerase I activity and an enzyme having DNA ligase activity;
• a third enzyme group that catalyzes a separation of two sister circular DNAs, wherein the third enzyme group comprises an enzyme having topoisomerase IV activity and/or an enzyme having topoisomerase III activity;
• a buffer;
• ATP;
• GTP, CTP and UTP;
• dNTP;
• a magnesium ion source;
• and
• an alkali metal ion source,
• wherein the circular DNA includes a replication origin sequence that can bind to an enzyme having DnaA activity;
• and
• (2) incubating the reaction mixture of (1) in a repeating temperature cycle of an incubation at 30° C. or higher and an incubation at 27° C. or lower.