Amino sugar metabolism in erythrocytes

Glucosamine 6‐phosphate deaminase in normal human erythrocytes

“…The substrate for the deaminase, glucosamine 6-phosphate, may be generated by four different reactions: (1) transfer of the amide group of glutamine to fructose 6-phosphate: (2) reversal of the deaminase reaction: ( 3 ) phosphorylation of glucosamine by hexokinase; and (4) deacetylation of N-acetylglucosamine 6phosphate. The mature erythrocyte has lost the ability to synthesize hexosamine-containing glycoconjugates and no longer contains significant amounts of the amidotransferase catalysing the first step in this process (reaction 1 above) (Kornfeld & Noll, 1968). It is possible, however, that trace amounts of glucosamine 6-phosphate are still being synthesized by the amidotransferase, and the presence of the deaminase, even at low activity levels, could then serve to return the glucosamine 6-phosphate to the glycolytic pathway for use in energy production.…”

“…It is possible, however, that trace amounts of glucosamine 6-phosphate are still being synthesized by the amidotransferase, and the presence of the deaminase, even at low activity levels, could then serve to return the glucosamine 6-phosphate to the glycolytic pathway for use in energy production. That the deaminase serves a synthetic role in mature erythrocytes appears improbable, since these cells do not have a requirement for hexosamine synthesis and do not possess the enzymes necessary for further processing of glucosamine 6-phosphate to UDP-N-acetylglucosamine (Kornfeld & Noll, 1968). The third potential source of the deaminase substrate is the phosphorylation of glucosamine.…”