Microbial growth on C1 compounds. Incorporation of C1 units into allulose phosphate by extracts of Pseudomonas methanica

Abstract

Incubation of cell-free extracts of methane- or methanol-grown P. methanica with [14c]formaldehyde and D-ribose 5-phosphate leads to incorporation of radioactivity into a non-volatile product, which has the chroma-tographic properties of a phosphorylated compound. Treatment of this reaction product with a phosphatase, followed by chromatography, shows the presence of two compounds whose chromatographic properties are consistent with their being free sugars. The minor component of the dephosphorylated products has been identified as fructose. The major component has been identified as allulose (psicose) on the basis of co-chromatography, co-crystallization of the derived phenylosazone and dinitrophenylosazone with authentic derivatives of allulose and behavior towards oxidation with bromine water. It is suggested that the bacterial extracts catalyze the condensation of a Cl unit identical with, or derived from, formaldehyde with ribose 5-phosphate to give allulose 6-phosphate. Testing of hexose phosphates and pentose phosphates as substrates has so far shown the reaction to be specific for ribose 5-phosphate. The condensation reaction is not catalyzed by extracts of methanol-grown Pseudomonas AM 1. A variant of the pentose phosphate cycle, involving this condensation reaction, is suggested as an explanation for the net synthesis of C3 compounds from Cl units by P. methanica.