Section 68
Chapter 67,188

Deoxycytidylate Aminohydrolase. Ii. Kinetic Properties. The Activatory Effect of Deoxycytidine Triphosphate and the Inhibitory Effect of Deoxythymidine Triphosphate *

Scarano, E.; Geraci, G.; Rossi, M.

Biochemistry 6(1): 192-201


ISSN/ISBN: 0006-2960
DOI: 10.1021/bi00853a031
Accession: 067187568

Download citation:  

Studies of the regulation of the activity of deoxycytidylate aminohydrolase have shown that deoxycytidine triphosphate (cCTP), the allosteric activator, and deoxythymidine triphosphate (dTTP), the allosteric inhibitor of the enzyme, are active only in the presence of a divalent cation. Experiments with Ca2+, Mg2+, and Mn2+ ions indicate that the true enzyme effectors are the complexes between the deoxynucleoside tri-phosphates and the metal ions. The dependence of the enzyme reaction on the substrate concentration is of an order higher than one in the buffers studied and the substrate concentration at half-enzyme saturation is dependent on the buffer. In the presence of 3 x 10-7 M dCTP the kinetics becomes of order one, while in the presence of increasing concentration of dTTP the apparent order of the reaction increases up to a limiting value of 4. The addition of dCTP removes the inhibition by dTTP. Likewise, high concentrations of glycerol activate the enzyme and high salt concentrations inhibit the enzyme.

PDF emailed within 0-6 h: $19.90