Identification of N -Acetylhexosamine 1-Kinase in the Complete Lacto- N -Biose I/Galacto- N -Biose Metabolic Pathway in Bifidobacterium longum

Abstract

ABSTRACT We have determined the functions of the enzymes encoded by the lnpB, lnpC , and lnpD genes, located downstream of the lacto- N -biose phosphorylase gene ( lnpA ), in Bifidobacterium longum JCM1217. The lnpB gene encodes a novel kinase, N -acetylhexosamine 1-kinase, which produces N -acetylhexosamine 1-phosphate; the lnpC gene encodes UDP-glucose hexose 1-phosphate uridylyltransferase, which is also active on N -acetylhexosamine 1-phosphate; and the lnpD gene encodes a UDP-glucose 4-epimerase, which is active on both UDP-galactose and UDP- N -acetylgalactosamine. These results suggest that the gene operon lnpABCD encodes a previously undescribed lacto- N -biose I/galacto- N -biose metabolic pathway that is involved in the intestinal colonization of bifidobacteria and that utilizes lacto- N -biose I from human milk oligosaccharides or galacto- N -biose from mucin sugars.