The metabolism of mannose by human erythrocytes has been investigated. Phosphorylation of mannose is achieved by an enzyme with electrophoretic mobility on starch gel indistinguishable from the glucose-phosphorylating enzyme. Mannose phosphorylation is competitively inhibited by glucose; glucose phosphorylation is competitively inhibited by mannose. The Ki values of inhibition are similar to the Km values for uninhibited phosphorylation. The normal average mannose-phosphorylating activity was found to be 0.69 U/g of Hb; the normal average glucose-phosphorylating activity was found to be 0.64 U/g of Hb. The ratio of mannose-phosphorylating activity to glucose-phosphorylating activity of a hemolysate prepared from the red cells of a subject with hexokinase deficiency was found to be within the normal range.
Ernest Beutler, Leslie Teeple