Sigmoid kinetics of human erythrocyte glucose-6-phosphate dehydrogenase

Adediran, S. A.

doi:10.1016/0003-9861(88)90198-1

Cited by 16 publications

(4 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There was no indication of any such complexities in these experiments. The pattern of converging lines confirms earlier reports that human Glc6 P dehydrogenase follows a sequential mechanism [14,15].…”

Section: Discussionsupporting

confidence: 89%

“…On the other hand, early studies of human Glc6 P dehydrogenase have left the kinetic mechanism a matter of controversy, both because of the conflicting conclusions of various investigators [11–13] and because of inherent doubts about Glc6 P dehydrogenase purified from pooled, expired blood from a genetically heterogeneous population. Adediran [14] proposed an ordered‐sequential mechanism with NADP + as the leading substrate, whereas Birke et al . [15] obtained quite different results from similar experiments.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Recombinant human glucose‐6‐phosphate dehydrogenase

Wang

Lam

et al. 2002

European Journal of Biochemistry

View full text Add to dashboard Cite

Cloning and over-expression of human glucose 6-phosphate dehydrogenase (Glc6P dehydrogenase) has for the first time allowed a detailed kinetic study of a preparation that is genetically homogeneous and in which all the protein molecules are of identical age. The steady-state kinetics of the recombinant enzyme, studied by fluorimetric initial-rate measurements, gave converging linear Lineweaver-Burk plots as expected for a ternary-complex mechanism. Patterns of product and dead-end inhibition indicated that the enzyme can bind NADP + and Glc6P separately to form binary complexes, suggesting a random-order mechanism. The K d value for the binding of NADP + measured by titration of protein fluorescence is 8.0 lM, close to the value of 6.8 lM calculated from the kinetic data on the assumption of a rapid-equilibrium random-order mechanism. Strong evidence for this mechanism and against either of the compulsory-order possibilities is provided by repeating the kinetic analysis with each of the natural substrates replaced in turn by structural analogues. A full kinetic analysis was carried out with deaminoNADP + and with deoxyglucose 6-phosphate as the alternative substrates. In each case the calculated dissociation constant upon switching a substrate in a random-order mechanism (e.g. that for NADP + upon changing the sugar phosphate) was indeed constant within experimental error as expected. The calculated rate constants for binding of the leading substrate in a compulsory-order mechanism, however, did not remain constant when the putative second substrate was changed. Previous workers, using enzyme from pooled blood, have variously proposed either compulsory-order or random-order mechanisms. Our study appears to provide unambiguous evidence for the latter pattern of substrate binding.Keywords: glucose-6-phosphate dehydrogenase; steady-state kinetics; rapid-equilibrium random-order mechanism; alternative substrate; product inhibition.Glucose-6-phosphate dehydrogenase (EC 1.l.1.49) in humans is an X-chromosome-linked housekeeping enzyme, vital for the life of every cell. It catalyses the oxidation of D-glucose 6-phosphate to D-glucono-d-lactone 6-phosphate in the first committed step of the pentose phosphate pathway, which provides cells with pentoses and reducing power in the form of NADPH. In red blood cells, this is the only source of NADPH required to protect the cells (via glutathione [1,2] and catalase [3,4]) against hydrogen peroxide and other oxidative damage. Accordingly, numerous Glc6P dehydrogenase mutations are associated with haemolytic anaemia [5].Until recently, detailed structural information was available only for the Glc6P dehydrogenase of Leuconostoc mesenteroides [6]. Extensive kinetic analysis of the NAD + -and NADP + -linked reactions for this bacterial Glc6P dehydrogenase [7][8][9][10] suggests different mechanisms for the two coenzymes. NADPH inhibition of the NADP + -linked reaction was competitive with respect to NADP + and noncompetitive with respect to Glc6P, whereas inhibition of the NAD + -...

show abstract

Section: Discussionsupporting

confidence: 89%

mentioning

confidence: 99%

Recombinant human glucose‐6‐phosphate dehydrogenase

Wang

Lam

et al. 2002

European Journal of Biochemistry

View full text Add to dashboard Cite

show abstract

“…Detailed kinetic analyses indicated that sheep brain cortex G6PD exhibit classical Michaelis-Menten kinetics (Figure 3). It has been reported in previous studies that many factors are affecting the kinetic properties of G6PD such as; pH, ionic strength, temperature, substrate concentration and properties of the enzyme (purified enzyme or crude extract) [14,15]. We have observed classical kinetics under our assay conditions.…”

Section: Kinetic Studiessupporting

confidence: 54%

Kinetic mechanism and some properties of glucose-6-phosphate dehydrogenase from sheep brain cortex

Ulusu

Sengezer

2012

Turk J Bioch

View full text Add to dashboard Cite

“…That the activity of G6PD is sensitive to the NADP + / NADPH ratio is not new. Comparisons of the reaction velocity vs. NADP + concentration were carried out in 1988, with very similar results [42]. In the study it was found that the relative reaction rate (a measured velocity over a defined maximal velocity ) increased as NADP + concentrations increased.…”

Section: The Reaction Equationmentioning

confidence: 78%

Predicting plasma ascorbate levels upon infusion and biochemical implications for glucose-6-phosphate dehydrogenase deficient patients

Cushing¹

View full text Add to dashboard Cite

Sigmoid kinetics of human erythrocyte glucose-6-phosphate dehydrogenase

Cited by 16 publications

References 20 publications

Recombinant human glucose‐6‐phosphate dehydrogenase

Recombinant human glucose‐6‐phosphate dehydrogenase

Kinetic mechanism and some properties of glucose-6-phosphate dehydrogenase from sheep brain cortex

Predicting plasma ascorbate levels upon infusion and biochemical implications for glucose-6-phosphate dehydrogenase deficient patients

Contact Info

Product

Resources

About