Document Type
Article
Publication Date
9-1-1993
Publication Title
Archives of Biochemistry and Biophysics
Abstract
Initial velocity studies obtained with alternative dinucleotide substrates for the 6-phosphogluconate dehydrogenase reaction suggest that the 2′-phosphate is critical for the optimum productive binding of the dinucleotide substrate. Initial velocity patterns obtained by varying 6-phosphogluconate at different fixed levels of NAD are nearly parallel with apparent competitive substrate inhibition by 6-phosphogluconate at pH 7 and below but intersect to the left of the ordinate at pH 8 and above. Dead-end inhibition studies indicate that the mechanism is random at all pH values. Data are interpreted in terms of a random mechanism with marked antagonism in the binding of NAD and 6-phosphogluconate at low pH. Deuterium isotope effects on V and V/K for either substrate are equal at pH 8, indicating that the kinetic mechanism is rapid equilibrium random. A decrease in the pH and the subsequent protonation of the active site general base or some other enzyme residue with a similar pK apparently results in the ineffective binding of NAD. The latter suggests either a link between the protonation state of this group and the conformation of the dinucleotide binding site or an interaction between the two.
Recommended Citation
Berdis, Anthony J. and Cook, Paul F., "The 2′-Phosphate of NADP Is Critical for Optimum Productive Binding to 6-Phosphogluconate Dehydrogenase from Candida Utilis" (1993). Chemistry Faculty Publications. 220.
https://engagedscholarship.csuohio.edu/scichem_facpub/220
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.
DOI
10.1006/abbi.1993.1460
Version
Postprint
Volume
305
Issue
2
Comments
This work was supported by grants to P.F.C. from NIH (GM 36799) and the Robert A. Welch Foundation (B-1031) and to A.J.B. from Sigma Xi (GIAR Award 9203).