In vitro synthesis of ornithine transcarbamylase

An in vitro system for the synthesis of ornithine transcarbamylase (OTCase) was established using iS-30 extract from E. coli MDS6-2(lambda) and DNA of a lambda transducing phage carrying argI and argF genes. This in vitro synthesis was completely dependent on the additon of DNA, and was sensitive to chloramphenicol and rifampicin. Radioisotopic analysis confirmed that the synthesized enzyme catalyzes the carbamylation of ornithine to citrulline. In the in vitro system the repression and derepression of OTCase synthesis could be observed by mixing iS-30 extracts prepared from argR+ and argR- cells. A remarkable maturation effect could be observed for the FFF enzyme, but not for the III enzyme. This system is considered to reflect the in vivo situation, and should therefore be useful for investigations on the regulation of OTCase synthesis in vivo.