Sugar metabolism in transketolase mutants of Escherichia coli

Abstract

This paper continues the description of transketolase mutants of E. coli; they are unable to grow on pentoses, but slightly 'leaky' with respect to their aromatic requirement. Several experiments have explored the degree of leakiness and shown it to be low. There is little conversion of radioactive xylose to carbon dioxide. The labeling of ribose in cells grown on [1 14C]glucose and [2 14C]glucose accords with its origin being chiefly by the oxidative pathway. A mutant lacking both transketolase and gluconate 6 phosphate dehydrogenase was constructed; it requires supplementation with pentose. Pentoses are inhibitory to growth of transketolase mutants, but high levels of pentose phosphates do not accumulate in this situation. Several experimental results are suggestive of regulation of metabolic flow in the oxidative branch of the hexose monophosphate shunt.