Carbohydrate metabolism in Antarctic birds' erythrocytes: Levels of IP5 and 2,3-DPG and their effect on chicken hexokinase activity

The aim of the present study is to show the possible implication of organic phosphate metabolites=namely inositol pentaphosphate (IP5) and 2,3-bisphosphoglycerate (2,3-DPG)=in the glucose metabolism displayed by birds erythrocytes. For this purpose, a preparation of hexokinase (HK) has been purified from chicken erythrocytes (RBC) by affinity chromatography in Sepharose-N-aminohexanoyl glucosamine and used for kinetic experiments. It has been shown that IP5 is a competitive inhibitor of HK in regard to Mg^, but not in regard to glucose and MgATP^. On the other hand, this preparation of HK is also competitively inhibited by ATP^. It has been found that the total intracellular content of Mg^ (2.76μmol/ml) is lower than the total value for the content of ATP and IP5 found in a standard packed red blood cell suspension.