APRT from erythrocytes of HGPRT deficient patients: Kinetic,regulatory and thermostability properties |
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Authors: | Crespillo Javier Llorente Pilar Argom´niz Luisa |
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Affiliation: | (1) Instituto de Investigaciones Biomédicas del C.S.I.C., Madrid, Spain |
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Abstract: | Adenine phosphoribosyltransferase (APRT) has been 1200-fold purified from erythrocytes of a patient with partial hipoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency, Propositus, and in those of a controlHPRT+, with 20% efficiency in both proteins and specific activity of 550 and 243 nmol/h/mgprotein. The specific activity determined in the Propositus enzyme was, in all purification steps, higher than that of the controlHPRT+. Significant changes were found in their thermal stabilities. Half inactivation times at each temperature studied are greater for the Propositus enzyme in the temperature interval 60–80°C. No significant difference has been observed in the affinity constants for adenine and PRPP substrates. Studies on inhibition by the reaction product suggest that AMP is a competitive inhibitor with respect to PRPP in both enzymes, with Ki values of 150 M in Propositus and 220 M in controlHPRT+. |
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Keywords: | APRT HGPRT deficiency erythrocytes purification kinetics |
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