Microbial growth on C1 compounds. 3. Distribution of radioactivity in metabolites of methanol-grown Pseudomonas AM1 after incubation with [14C]methanol and [14C]bicarbonate

Abstract

The distribution of radioactivity in glycine serum, phosphoglyceric acid and malic acid isolated from methanol-grown Pseudomonas AM I after incubation with [C14]methanol or [C14]biocarbonate has been investigated. The data indicate that the carboxyl group of glycine is mainly derived from CO2, and the methylene C from methanol. The hydroxymethyl group of serine is derived mainly from methanol, whereas the distribution of radioactivity between C-1 and C 2 of serine is the same under all conditions as that between C-1 and C-2 of glycine. The labelling patterns of serine and malate are consistent with the formation of malate by carboxylation of a C3 fragment derived from serine, rather than with the reverse reaction. Two possible schemes for synthesis of cell constituents from methanol are outlined. Both schemes implicate hydroxymethylation of glycine to give serine as the major step in the synthesis of C3 compounds. Alternative means whereby the glycine necessary for such a reaction might be made from methanol are discussed.