TY - JOUR
T1 - Convergent pathways for utilization of the amino sugars N- acetylglucosamine, N-acetylmannosamine, and N-acetylneuraminic acid by Escherichia coli
AU - Plumbridge, Jacqueline
AU - Vimr, Eric
PY - 1999/1
Y1 - 1999/1
N2 - N-Acetylglucosamine (GlcNAc) and N-acetylneuraminic acid (NANA) are good carbon sources for Escherichia coli K-12, whereas N-acetylmannosamine (ManNAc) is metabolized very slowly. The isolation of regulatory mutations which enhanced utilization of ManNAc allowed us to elucidate the pathway of its degradation. ManNAc is transported by the manXYZ-encoded phosphoenolpyruvate-dependent phosphotransferase system (PTS) transporter producing intracellular ManNAc-6-P. This phosphorylated hexosamine is subsequently converted to GlcNAc-6-P, which is further metabolized by the nagBA-encoded deacetylase and deaminase of the GlcNAc-6-P degradation pathway. Two independent mutations are necessary for good growth on ManNAc. One mutation maps to talc, and mutations in this gene are known to enhance the expression of manXYZ. The second regulatory mutation was mapped to the nanAT operon, which encodes the NANA transporter and NANA lyase. The combined action of the nanAT gene products converts extracellular NANA to intracellular ManNAc. The second regulatory mutation defines an open reading frame (ORF), called yhcK, as the gene for the repressor of the nan operon (nanR). Mutations in the repressor enhance expression of the nanAT genes and, presumably, three distal, previously unidentified genes, yhcJIH. Expression of just one of these downstream ORFs, yhcJ, is necessary for growth on ManNAc in the presence of an mlc mutation. The yhcJ gene appears to encode a ManNAc- 6-P-to-GlcNAc-6-P epimerase (nanE). Another putative gene in the nan operon, yhcI, likely encodes ManNAc kinase (nanK), which should phosphorylate the ManNAc liberated from NANA by the NanA protein. Use of NANA as carbon source by E. coli also requires the nagBA gene products. The existence of a ManNAc kinase and epimerase within the nan operon allows us to propose that the pathways for dissimilation of the three amino sugars GlcNAc, ManNAc, and NANA, all converge at the step of Glc-NAc-6-P.
AB - N-Acetylglucosamine (GlcNAc) and N-acetylneuraminic acid (NANA) are good carbon sources for Escherichia coli K-12, whereas N-acetylmannosamine (ManNAc) is metabolized very slowly. The isolation of regulatory mutations which enhanced utilization of ManNAc allowed us to elucidate the pathway of its degradation. ManNAc is transported by the manXYZ-encoded phosphoenolpyruvate-dependent phosphotransferase system (PTS) transporter producing intracellular ManNAc-6-P. This phosphorylated hexosamine is subsequently converted to GlcNAc-6-P, which is further metabolized by the nagBA-encoded deacetylase and deaminase of the GlcNAc-6-P degradation pathway. Two independent mutations are necessary for good growth on ManNAc. One mutation maps to talc, and mutations in this gene are known to enhance the expression of manXYZ. The second regulatory mutation was mapped to the nanAT operon, which encodes the NANA transporter and NANA lyase. The combined action of the nanAT gene products converts extracellular NANA to intracellular ManNAc. The second regulatory mutation defines an open reading frame (ORF), called yhcK, as the gene for the repressor of the nan operon (nanR). Mutations in the repressor enhance expression of the nanAT genes and, presumably, three distal, previously unidentified genes, yhcJIH. Expression of just one of these downstream ORFs, yhcJ, is necessary for growth on ManNAc in the presence of an mlc mutation. The yhcJ gene appears to encode a ManNAc- 6-P-to-GlcNAc-6-P epimerase (nanE). Another putative gene in the nan operon, yhcI, likely encodes ManNAc kinase (nanK), which should phosphorylate the ManNAc liberated from NANA by the NanA protein. Use of NANA as carbon source by E. coli also requires the nagBA gene products. The existence of a ManNAc kinase and epimerase within the nan operon allows us to propose that the pathways for dissimilation of the three amino sugars GlcNAc, ManNAc, and NANA, all converge at the step of Glc-NAc-6-P.
UR - http://www.scopus.com/inward/record.url?scp=0032929297&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032929297&partnerID=8YFLogxK
U2 - 10.1128/jb.181.1.47-54.1999
DO - 10.1128/jb.181.1.47-54.1999
M3 - Article
C2 - 9864311
AN - SCOPUS:0032929297
SN - 0021-9193
VL - 181
SP - 47
EP - 54
JO - Journal of bacteriology
JF - Journal of bacteriology
IS - 1
ER -