Growth of Paracoccus denitrificans on [2, 3- 13 C]succinate and [1, 4- 13 C]succinate - II. Isoleucine biosynthesis

Abstract

Paracoccus denitrificans was grown on either [2, 3- 13 C]succinate or [1, 4- 13 C]succinate, and extracts were analysed by using gas chroma­tography-mass spectrometry. The distribution of label in isoleucine indicated that the 2-ketobutyrate required for isoleucine biosynthesis was mainly produced from pyruvate by 2-keto-acid chain elongation (i. e. the 'pyruvate elongation pathway’). Approximately 10% of isoleucine was produced by a second pathway involving propionyl CoA. Threonine and glutamate were not utilized by P. denitrificans as a source of 2-ketobutyrate production for isoleucine biosynthesis under the growth conditions used.