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Activation by calcium of AMP deaminase from the human red cell
Author(s) -
Almaraz Laura,
García-Sancho Javier
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)80575-7
Subject(s) - chemistry , dilution , calcium , enzyme , red cell , cooperativity , biochemistry , red blood cell , calmodulin , biophysics , chromatography , biology , medicine , physics , organic chemistry , thermodynamics
We have investigated the effects of Ca 2+ on AMP deaminase from human red cells. At variance with the other known modulators, Ca 2+ increased the apparent affinity for AMP without modifying the characteristic positive cooperativity of the enzyme towards the substrate. Ca 2+ sensitivity was not modified by dialysis, but dilution of the haemolysate produced an activation of the enzyme similar to that induced by Ca 2+ . Simultaneously, the Ca 2+ dependence was lost. The sensitivity to other modulators, such as ATP, diphosphoglycerate or phosphate, was not modified by dilution. Partial purification of the enzyme produced the same effects as haemolysate dilution. These results may be interpreted to mean that Ca 2+ acts by antagonizing an endogenous inhibitor present in red cell lysates.