Koji Ikura

2,3-bisphosphoglycerate in erythroid cells

Abstract 2,3-Bisphosglycerate accumulates in erythrocytes where it facilitates the supply of oxygen to the tissues by binding to hemoglobin. The concentration of 2,3-bisphosphoglycerate changes in a number of physiological and pathological conditions and during animal ontogeny. During erythroid differentiation in bone marrow the synthesis of 2,3-bisphosphogylcerate is induced. The regulation of 2,3-bisphosphogylcerate metabolism is beginning to be understood.

Comparative studies of the enzymes involved in 2,3-bisphosphoglycerate metabolism of rabbit erythrocytes and muscle cells.

1. 1. The enzymes participating in 2,3-bisphosphoglycerate metabolism were purified from erythrocytes and muscle cells of rabbit (Oryctolagus coniculus domesticus) in order to clarify why this compound accumulates in erythrocytes but not in tissue cells. 2. 2. Two irreversible reactions, synthesis and breakdown of 2,3-bisphosphoglycerate, are catalyzed by one multifunctional enzyme in erythrocytes. 3. 3. Muscle cells have a novel enzyme, 2,3-bisphosphoglycerate phosphatase, which has never been found before in mammalian erythrocytes and which may be mainly responsible for keeping this compound at low levels.

The microdetermination of 2,3-diphosphoglycerate

Abstract A procedure for microestimation of 2,3-diphosphoglycerate, utilizing its role as coenzyme in the phosphoglycerate mutase reaction is described. The coenzymic activity was determined by assaying phosphoglycerate mutase polarimetrically without a coupled enzyme. This method is applicable to samples containing as little as 0.002 μmole of 2,3-diphosphoglycerate/ml. The content in various biological extracts was determined.

Regulation of protein synthesis in rabbit reticulocyte lysates by 2,3-bisphosphoglycerate

Abstract 2,3-Bisphosphoglycerate was the most potent effector of glycolytic intermediates tested for their effects on protein synthesis in gel-filtered lysates from rabbit reticulocytes. 2,3-Bisphosphoglycerate at low levels was stimulatory but became inhibitory at high levels. Both effects were dependent on Mg 2+ concentrations. The higher the concentration of Mg 2+ , the higher the concentration of 2,3-bisphosphoglycerate required for maximal activation. 2,3-Bisphosphoglycerate concentrations required to exhibit an inhibitory effect increased as Mg 2+ concentration increased. Both effects of 2,3-bisphosphoglycerate are discussed in terms of regulation of hemoglobin synthesis during maturation of erythroid cells.

Activity and gene expression of transglutaminase in guinea pig liver during the postnatal growing phase

During the postnatal growing phase from birth to 7 weeks old, the cytosolic transglutaminase activity of guinea pig liver increased 3.8‐fold. The enzyme activity in the particulate fraction increased slightly. Immunoblot analyses showed that the postnatal increase in the activity was correlated with an increase in the enzyme protein. The quantity of mRNA of the liver transglutaminase did not change significantly during the postnatal growing phase examined. These results indicated that transglutaminase may be involved in the postnatal development of guinea pig liver and that the amount of transglutaminase in the postnatal liver may be controlled post‐transcriptionally.