Characterization of the first described mutation of human red blood cell phosphoglycerate mutase

In a patient with clinical diagnosis of Hereditary Spherocytosis and partial deficiency (50%) of red blood cell phosphoglycerate mutase (PGAM) activity, we have recently reported [A. Repiso, P. Perez de la Ossa, X. Aviles, B. Oliva, J. Junca, R. Oliva, E. Garcia, J.L.L. Vives-Corrons, J. Carreras, F. Climent, Red blood cell phosphoglycerate mutase. Description of the first human BB isoenzyme mutation, Haematologica, 88 (2003) (03) ECR07] the first described mutation of type B PGAM subunit that as a dimer constitutes the PGAM (EC 5.4.2.1) isoenzyme present in red blood cells. The mutation is the substitution c.690G > A (p.Met230Ile). In this report, we show that the mutated PGAM possesses an abnormal behaviour on ion-exchange chromatography and is more thermo-labile that the native enzyme. We also confirm that, similar to the PGAM isoenzymes from other sources, the BB-PGAM from human erythrocytes has a ping pong or phosphoenzyme mechanism, and that the mutation does not significantly change the K-m and K-i values, and the optimum pH of the enzyme. The increased instability of the mutated enzyme can account for the decreased PGAM activity in patient's red blood cells. However, the implication of a change of the k(cat) produced by the mutation cannot be discarded, since we could not determine the k(cat) value of the mutated PGAM. (c) 2004 Elsevier B.V. All rights reserved.