De novo purine synthesis in vegetative cells and myxospores of Myxococcus xanthus.

This study was designed to determine whether vegetative cells and myxospores of Myxococcus xanthus were capable of classical de novo purine biosynthesis. To answer this question, vegetative and myxospore extracts of M. xanthus FBa were tested for their ability to synthesize the second de novo intermediate, 5'-phosphoribosylglycinamide, from beginning precursors either by way of phosphoribosyl-pyrophosphate amido transferase (EC 2.4.2.14) or ribose-5-phosphate amino transferase. Both the amido and amino transferase routes occurred in both types of extracts, and both enzymes appear to be present at about the same level (per milligram of protein) in vegetative cells, myxospores, and in a bacterial prototype, Salmonella typhimurium. The dose response of the vegetative and myxospore forms of both enzymes towards adenosine 5'-monophosphate (AMP) and guanosine 5'-monophosphate (GMP) suggests that the allosteric structure of both enzymes is changed little by sporulation. Both enzymes were inhibited to varying degrees by a variety of purine nucleotides besides AMP, GMP, and 3':5' cyclic AMP.