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Oxidative decarboxylation of 6-phosphogluconate by 6-phosphogluconate dehydrogenase proceeds by a stepwise mechanism with NADP and APADP as oxidants.
Biochemistry. 1998 Sep 08; 37(36):12596-602.B

Abstract

Primary kinetic deuterium, 13C, and multiple deuterium/13C-isotope effects on V/K6PG have been measured for the Candida utilis (cu) and sheep liver (sl) 6-phosphogluconate dehydrogenases (6PGDH). With NADP as the dinucleotide substrate, the following values of D(V/K6PG), 13(V/K6PG)H, and 13(V/K6PG)D were measured at pH 8 for cu6PGDH (sl6PGDH): 1.57 +/- 0.08 (1.87 +/- 0.10), 1.0209 +/- 0.0005 (1.0059 +/- 0.000 10), 1.0158 +/- 0.0001 (1.0036 +/- 0.0008). With APADP as the dinucleotide substrate, values for the above isotope effects at pH 8 are as follows: 2.98 +/- 0.08 (2.47 +/- 0.06), 1. 0106 +/- 0.0002 (1.0086 +/- 0.000 09), and 0.9934 +/- 0.0003 (0.9950 +/- 0.0003). Results indicate the oxidative decarboxylation of 6PG to the 1,2-enediol of ribulose 5-phosphate proceeds via a stepwise mechanism with hydride transfer preceding decarboxylation in all cases. The inverse 13C-isotope effect observed with APADP and 6PG-3d may reflect a preequlibrium isotope effect on the binding of 6PG preceding hydride transfer. Deuterium-isotope effects on V, V/KNADP, and V/K6PG are identical at all pHs and for both enzymes. The primary deuterium-isotope effect on V/K6PG for both enzymes is constant at pH values below the pK in the pH profile for V/K6PG, and decreases as the pH increases. Data suggest the development of rate limitation by a step or steps other than the hydride-transfer step as the pH is increased.

Authors+Show Affiliations

Department of Chemistry and Biochemistry, University of Oklahoma, Norman 73019, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9730832

Citation

Hwang, C C., et al. "Oxidative Decarboxylation of 6-phosphogluconate By 6-phosphogluconate Dehydrogenase Proceeds By a Stepwise Mechanism With NADP and APADP as Oxidants." Biochemistry, vol. 37, no. 36, 1998, pp. 12596-602.
Hwang CC, Berdis AJ, Karsten WE, et al. Oxidative decarboxylation of 6-phosphogluconate by 6-phosphogluconate dehydrogenase proceeds by a stepwise mechanism with NADP and APADP as oxidants. Biochemistry. 1998;37(36):12596-602.
Hwang, C. C., Berdis, A. J., Karsten, W. E., Cleland, W. W., & Cook, P. F. (1998). Oxidative decarboxylation of 6-phosphogluconate by 6-phosphogluconate dehydrogenase proceeds by a stepwise mechanism with NADP and APADP as oxidants. Biochemistry, 37(36), 12596-602.
Hwang CC, et al. Oxidative Decarboxylation of 6-phosphogluconate By 6-phosphogluconate Dehydrogenase Proceeds By a Stepwise Mechanism With NADP and APADP as Oxidants. Biochemistry. 1998 Sep 8;37(36):12596-602. PubMed PMID: 9730832.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Oxidative decarboxylation of 6-phosphogluconate by 6-phosphogluconate dehydrogenase proceeds by a stepwise mechanism with NADP and APADP as oxidants. AU - Hwang,C C, AU - Berdis,A J, AU - Karsten,W E, AU - Cleland,W W, AU - Cook,P F, PY - 1998/9/9/pubmed PY - 1998/9/9/medline PY - 1998/9/9/entrez SP - 12596 EP - 602 JF - Biochemistry JO - Biochemistry VL - 37 IS - 36 N2 - Primary kinetic deuterium, 13C, and multiple deuterium/13C-isotope effects on V/K6PG have been measured for the Candida utilis (cu) and sheep liver (sl) 6-phosphogluconate dehydrogenases (6PGDH). With NADP as the dinucleotide substrate, the following values of D(V/K6PG), 13(V/K6PG)H, and 13(V/K6PG)D were measured at pH 8 for cu6PGDH (sl6PGDH): 1.57 +/- 0.08 (1.87 +/- 0.10), 1.0209 +/- 0.0005 (1.0059 +/- 0.000 10), 1.0158 +/- 0.0001 (1.0036 +/- 0.0008). With APADP as the dinucleotide substrate, values for the above isotope effects at pH 8 are as follows: 2.98 +/- 0.08 (2.47 +/- 0.06), 1. 0106 +/- 0.0002 (1.0086 +/- 0.000 09), and 0.9934 +/- 0.0003 (0.9950 +/- 0.0003). Results indicate the oxidative decarboxylation of 6PG to the 1,2-enediol of ribulose 5-phosphate proceeds via a stepwise mechanism with hydride transfer preceding decarboxylation in all cases. The inverse 13C-isotope effect observed with APADP and 6PG-3d may reflect a preequlibrium isotope effect on the binding of 6PG preceding hydride transfer. Deuterium-isotope effects on V, V/KNADP, and V/K6PG are identical at all pHs and for both enzymes. The primary deuterium-isotope effect on V/K6PG for both enzymes is constant at pH values below the pK in the pH profile for V/K6PG, and decreases as the pH increases. Data suggest the development of rate limitation by a step or steps other than the hydride-transfer step as the pH is increased. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/9730832/Oxidative_decarboxylation_of_6_phosphogluconate_by_6_phosphogluconate_dehydrogenase_proceeds_by_a_stepwise_mechanism_with_NADP_and_APADP_as_oxidants_ L2 - https://dx.doi.org/10.1021/bi980611s DB - PRIME DP - Unbound Medicine ER -