A hidden metabolic pathway exposed

摘要

Before reading the report by Sydney Kustu's research group published in a recent issue of PNAS, I would have seriously doubted that discovery of a novel pathway for pyrimidine catabolism in Escherichia coli K12 was something that was still possible today. After all of the years of exhaustive genetic and biochemical studies, almost a decade past completion of the genome, after innumerable annotation and reannotation efforts, metabolic modeling, and systematic functional genomics studies, a completely novel pathway was found? Although functional roles of many E. coli genes (at least 20%) are still unknown, these remaining y genes are largely perceived as potential off-mainstream players in some obscure areas of metabolism or, even more likely, in nonmetabolic processes. Therefore, a string of eight y genes encoding an entire pathway in the very center of the E. coli metabolic map felt like it was too big a skeleton to be hidden in a closet.