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Interaction of ATP with erythroblast glucose‐6‐phosphate dehydrogenase
Author(s) -
Ninfali Paolino,
Baronciani Luciano
Publication year - 1996
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/15216549600201411
Subject(s) - guanosine diphosphate , gtp' , cooperativity , cooperative binding , enzyme , dehydrogenase , nad+ kinase , biochemistry , chemistry , uncompetitive inhibitor , adenosine triphosphate , allosteric regulation , non competitive inhibition , guanosine triphosphate
ATP, complexed with magnesium and as free anion, binds to rabbit erythroblasts glucose‐6‐phosphate dehydrogenase (G6PD) inducing significant structural transitions in the enzyme, revealed by a different heat stability. ATP4‐ facilitates the process of thermal inactivation by inducing the presence of thermolable forms. On the contrary, ATP‐Mg protects the enzyme from thermal inactivation. The protection is significant but less marked than that shown by NADP. Kinetic studies indicate a different type of binding between ATP‐Mg and ATP4‐. Uncomplexed ATP is a competitive inhibitor vs NADP or G6P and it shows a positive cooperative effect. ATP‐Mg is an uncompetitive inhibitor vs G6P and competitive vs NADP and it shows a negative cooperativity. A similar behaviour is also shown by complexed and free CTP and GTP.