SUBSTANCES STIMULATING GLUCOSE CATABOLISM BY THE OXIDATIVE REACTIONS OF THE PENTOSE PHOSPHATE PATHWAY IN HUMAN ERYTHROCYTES*

Abstract

Mature human erythrocytes possess the enzymes necessary to catabolize glucose to CO2 via pentose phosphate pathway or to lactic acid via the Emb- den-Meyerhof pathway. These cells are deficient in certain enzymes of the tricarboxylic acid cycle. In the non-nucleated red cells, the oxidative reac- tions of pentose phosphate pathway appear to be the sole mechanism for glucose conversion to CO2 and for the generation of TPNH (2, 3). Several investigators have suggested that a major factor in the control of the rate of glucose catabo- lism via the pentose phosphate pathway is the meta- bolic demand for TPNH (4-6). It has been dem- onstrated that addition of dyes capable of acting as electron acceptors from TPNH (i.e., methylene blue, phenazine methosulphate, pyocyanin) in- creases the rate of activity of this pathway in eryth- rocytes, liver slices and mammary glands (7-9). Stimulation of the pentose phosphate pathway by pyruvate in bovine corneal epithelium, by insulin in rat mammary tissue, and by ammonium salts in yeasts has been ascribed to supply of substrates requiring TPNH for their metabolism or to stim- ulation of enzyme systems which utilize TPNH (8, 10-12).