The effect of pH and temperature on the kinetics of native and altered glycogen phosphorylase

Kasvinsky, Peter J.; Meyer, William L.

doi:10.1016/0003-9861(77)90268-5

Cited by 34 publications

(27 citation statements)

References 42 publications

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“…The differences in the profiles also are not due to a perturbation of the buffer pH by the solvent because, as is seen in Figure 3C, the same shift in the acidic limb is seen in Tris-imidazole buffer. Clearly, the changes seen here are due to a perturbation of some group on the enzyme that is important for the catalytic reaction rather than the binding of the substrates or activators because all effectors used here should be saturating according to the results reported by Kasvinsky & Meyer (1977) and Hollo et al (1966). Figure 4A shows the effect of 1,2-dimethoxyethane on the inhibition by 1,5-gluconolactone.…”

Section: Resultsmentioning

confidence: 74%

Effects of 1,2-dimethoxyethane on the catalytic and coenzyme properties of glycogen phosphorylase

Uhing¹,

Lentz²,

Graves³

1981

Biochemistry

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Dimethoxyethane, a good activator of phosphorylase b, has been used to study mechanisms of phosphorylase activation and the catalytic reaction. Activation can be explained best by an alteration of the allosteric equilibrium in favor of the active R conformation. Lesser effects are seen with phosphorylase a, and activation does not alter appreciably the equilibrium between the dimeric and tetrameric forms. With 20% 1,2-dimethoxyethane, the Vm value of phosphorylase b is 74% of that obtained in the presence of adenosine monophosphate. In the presence of 10% 1,2-dimethoxyethane, the Ki value for glucose inhibition is increased 3-fold, but inhibition by 1,5-gluconolactone is increased. The allosteric activation of glycogen phosphorylase results in a change in pK1 for the pH-activity profile. The formation of the dianionic form of the phosphoryl group of the coenzyme, pyridoxal phosphate, may account for this change. By analogy to the effects of anions and a change in dielectric on the acid hydroylsis of glucose 1-phosphate, it is suggested that the dianion of the coenzyme could stabilize the developing positive charge of an oxonium ion intermediate. Dimethoxyethane also affects the interaction of pyridoxal phosphate with phosphorylase. It influences the rates of both resolution and reconstitution. Good preparations of apophosphorylase a can be made by using 1,2-dimethoxyethane in the resolution medium.

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Section: Resultsmentioning

confidence: 74%

Effects of 1,2-dimethoxyethane on the catalytic and coenzyme properties of glycogen phosphorylase

Uhing¹,

Lentz²,

Graves³

1981

Biochemistry

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“…1 (36). This work also showed that the dianion of inorganic phosphate is the true substrate and that a histidine residue would account for the alkaline limb of the activity vs pH profiles with a pK2 of 7.1.…”

Section: Chemical Studiesmentioning

confidence: 78%

The Structures and Related Functions of Phosphorylase a

Fletterick¹,

Madsen²

1980

Annu. Rev. Biochem.

205

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“…Values with different superscripts are significantly different (P Ͻ 0.05). chemical form of P i from the monoprotonated form, which is the active substrate for Phos a , to the diprotonated form, which does not act as a substrate for Phos a (12). Changes in muscle NH 3 suggest that at Ͼ10 s of exercise IMP was accumulating from the deamination of AMP, which is also thought to allosterically stimulate Phos a (3).…”

Section: Regulation Of Fuel Selection In White Musclementioning

confidence: 98%

“…The transformation between Phos b and Phos a is regulated at the contractile level through Ca 2ϩ release from the sarcoplasmic reticulum. Decreases in intracellular pH (pH i ) affect the transformation of Phos by inhibiting Phos kinase (4) and affect substrate availability by shifting the speciation of P i (12). To our knowledge, the transformation of Phos has not been examined in trout white muscle during high-intensity exercise.…”

mentioning

confidence: 95%

Glycogen phosphorylase and pyruvate dehydrogenase transformation in white muscle of trout during high-intensity exercise

Richards¹,

Heigenhauser

Wood³

2002

American Journal of Physiology-Regulatory, Integrative and Comp

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We examined the regulation of glycogen phosphorylase (Phos) and pyruvate dehydrogenase (PDH) in white muscle of rainbow trout during a continuous bout of high-intensity exercise that led to exhaustion in 52 s. The first 10 s of exercise were supported by creatine phosphate hydrolysis and glycolytic flux from an elevated glycogenolytic flux and yielded a total ATP turnover of 3.7 micromol x g wet tissue(-1) x s(-1). The high glycolytic flux was achieved by a large transformation of Phos into its active form. Exercise performed from 10 s to exhaustion was at a lower ATP turnover rate (0.5 to 1.2 micromol x g wet tissue(-1) x s(-1)) and therefore at a lower power output. The lower ATP turnover was supported primarily by glycolysis and was reduced because of posttransformational inhibition of Phos by glucose 6-phosphate accumulation. During exercise, there was a gradual activation of PDH, which was fully transformed into its active form by 30 s of exercise. Oxidative phosphorylation, from PDH activation, only contributed 2% to the total ATP turnover, and there was no significant activation of lipid oxidation. The time course of PDH activation was closely associated with an increase in estimated mitochondrial redox (NAD(+)-to-NADH concentration ratio), suggesting that O2 was not limiting during high-intensity exercise. Thus anaerobiosis may not be responsible for lactate production in trout white muscle during high-intensity exercise.

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The effect of pH and temperature on the kinetics of native and altered glycogen phosphorylase

Cited by 34 publications

References 42 publications

Effects of 1,2-dimethoxyethane on the catalytic and coenzyme properties of glycogen phosphorylase

Effects of 1,2-dimethoxyethane on the catalytic and coenzyme properties of glycogen phosphorylase

The Structures and Related Functions of Phosphorylase a

Glycogen phosphorylase and pyruvate dehydrogenase transformation in white muscle of trout during high-intensity exercise

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