Regulation and kinetics of glucose 6-phosphate dehydrogenase from Candida utilis

Afolayan, Adeyinka

doi:10.1021/bi00772a022

Cited by 28 publications

(17 citation statements)

References 32 publications

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“…The regulatory mechanisms by which the HMS is adjusted to the needs of lipid synthesis may include the small increases in 6-phosphogluconate dehydrogenase and possibly glucose-6-phosphate dehydrogenase that have been observed in the sympathetic ganglia at about the appropriate developmental stage (Kauffman et al, 1983 and unpublished observations quoted by Larrabee, 1985). However, it is reasonable to assume that the regulation is mostly more direct, through the removal by lipid synthesis of NADPH, which has been shown to inhibit glucose-6-phosphate (Afolayan, 1972;Eggleston and Krebs, 1974), and the formation of NADP+, which is needed in the dehydrogenase steps of the shunt (DiPietro and Weinhouse, 1959;Kauffman et al, 1969). Thus, if in early development the oxidation of NADPH occurs only or predominately by lipid synthesis, the two rates would be tightly and obligatorily coupled.…”

Section: Resultsmentioning

confidence: 99%

Ontogeny of Glucose Metabolism in Sympathetic Ganglia of Chickens. Concurrence of Maximum Rates in the Hexosemonophosphate Shunt and in Synthesis of Lipids but Not of Ribonucleic Acid

Larrabee¹

1987

Journal of Neurochemistry

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Chains of sympathetic ganglia were excised from the lumbar region of white Leghorn chicken embryos, 8-19 days of age, and incubated, usually for 5 h, at 36 degrees C in a bicarbonate-buffered physiological salt solution containing [U-14C]glucose, [1-14C]glucose, [6-14C]glucose, or [5-3H]uridine. Lipid synthesis was measured by the incorporation of 14C into lipids, and RNA synthesis by the accumulation of 3H into macromolecules. The ratio of 14C put out in CO2 during the second hour of incubation in the presence of [1-14C]glucose to that with [6-14C]glucose was used as an index of activity in the hexosemonophosphate shunt (HMS). Both the rate of lipid synthesis and activity in the HMS reached well-defined maxima at about 11 days of embryonic age. There was no evidence of a similar rise and fall of RNA synthesis during the ages studied. Estimates of the rate of NADPH production by the HMS at near-peak lipid synthesis varied over a twofold range that included the rate needed for the observed lipid synthesis. The results thus support, quantitatively as well as qualitatively, the supposition that the HMS is accelerated during development to sustain lipid synthesis.

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Section: Resultsmentioning

confidence: 99%

Ontogeny of Glucose Metabolism in Sympathetic Ganglia of Chickens. Concurrence of Maximum Rates in the Hexosemonophosphate Shunt and in Synthesis of Lipids but Not of Ribonucleic Acid

Larrabee¹

1987

Journal of Neurochemistry

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“…* It is worth noting here that some care must be exercised in the choice of buffers used for lunetic studies. A number of investigators have reported sigmoid kinetics (5,6,217,218) or complex pH effects on kinetic parameters (20,175) for human erythrocyte GGPD using Tris-borate buffer. Although one group of investigators claimed that the use of borate did not affect kinetic constants (20), others reported that borate inhibited human erythrocyte GGPD and led to a sigmoid relationship between catalytic activity and NADP' concentration (394,398).…”

Section: Effects Of Ph Ionic Strength and Temperaturementioning

confidence: 99%

Glucose‐6‐Phosphate Dehydrogenases

1979

Advances in Enzymology - And Related Areas of Molecular Biology

105

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“…Random order is unusual for any dehydrogenase, and has not been observed for any other glucose-6-phosphate dehydrogenase. The enzyme from human erythrocyte (16), Escherichia coli (17), Candida utilis (18) and Leuconostoc mesenteroides (1 9) yield kinetic data which are consistent with a compulsory ordered addition of substrates, although random order was not ruled out in these cases with the exception of the enzyme from Leuconostoc mesenteroides (19). Most other NADP+ dehydro-genases have compulsory ordered mechanisms with the coenzyme binding first (20).…”

Section: Discussionmentioning

confidence: 99%

Kinetics and Control of Bovine Adrenal Glucose‐6‐phosphate Dehydrogenase

Schachet

Squire

1976

International Journal of Peptide and Protein Research

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Michaelis‐Menten kinetics are observed in studies of highly purified bovine adrenal glucose‐6‐phosphate dehydrogenase at pH 8.0 in 0.1 M bicine. The Km for NADP+ is 3.8 μM and for glucose‐6‐phosphate, 61 μM. At pH 6.9, Km for NADP+ increases to 6.5 μM. The enzyme is inhibited by NADPH both at pH 6.8 and at 8.0 with a Kip of 2.36 μM at pH 8.0. Inhibition is competitive with respect to both substrates implying that addition of substrates is random ordered. The data are also interpreted in terms of “reducing charge”, the mole fraction of coenzyme in the reduced form. This appears to be the major mechanism for regulation of the pentose shunt. D‐glucose, oxidized by the enzyme at a very slow rate, is also a competitive inhibitor for the natural substrate with a Ki of 0.29 M. Phosphate is a competitive inhibitor for glucose‐6‐phosphate oxidation but both phosphate and sulfate accelerate glucose oxidation suggesting a common binding site for the two anions and the phosphate of the natural substrate. While binding of ACTH to our enzyme preparations has been observed, we have not been able, in spite of repeated attempts, to demonstrate augmentation of the activity of the enzyme by the addition of ACTH.

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Regulation and kinetics of glucose 6-phosphate dehydrogenase from Candida utilis

Cited by 28 publications

References 32 publications

Ontogeny of Glucose Metabolism in Sympathetic Ganglia of Chickens. Concurrence of Maximum Rates in the Hexosemonophosphate Shunt and in Synthesis of Lipids but Not of Ribonucleic Acid

Ontogeny of Glucose Metabolism in Sympathetic Ganglia of Chickens. Concurrence of Maximum Rates in the Hexosemonophosphate Shunt and in Synthesis of Lipids but Not of Ribonucleic Acid

Glucose‐6‐Phosphate Dehydrogenases

Kinetics and Control of Bovine Adrenal Glucose‐6‐phosphate Dehydrogenase

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