Effects of sulfhydryl reagents on synthetic and hydrolytic activities of multifunctional glucose-6-phosphatase

Colilla, William; Nordlie, Robert C.

doi:10.1016/0005-2744(73)90031-4

Cited by 20 publications

(5 citation statements)

References 20 publications

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“…These agents give only partial protection for NADPH cyt c reductase activity and no protection for G-6-Pase activity. This is a noteworthy finding since the latter two enzymes require thiol groups for their activity (21,4).…”

Section: Enzyme Activities and Their Inactivationmentioning

confidence: 94%

Endoplasmic reticulum marker enzymes in Golgi fractions--what does this mean?

Howell¹,

Ito²,

Palade³

1978

The Journal of Cell Biology

133

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NADPH cytochrome c (cyt c ) reductase and glucose-6-phosphatase, two enzymes thought to be restricted to the endoplasmic reticulum (ER) and widely used as ER markers, are present in isolated Golgi fractions assayed immediately after their isolation. Both enzymes are rapidly inactivated in fractions stored at 0~ in 0.25 M sucrose, conditions which do not affect the activity of other enzymes in the same preparation. The inactivation process was shown to be dependent on time and protein concentration and could be prevented by EDTA and catalase. Morphological evidence shows that extensive membrane damage occurs parallel with the inactivation. Taken together with the immunological data in the companion paper, the findings indicate that the enzymes NADPH cyt c reductase and probably glucose-6-phosphate are indigenous components of Golgi membranes.

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Section: Enzyme Activities and Their Inactivationmentioning

confidence: 94%

Endoplasmic reticulum marker enzymes in Golgi fractions--what does this mean?

Howell¹,

Ito²,

Palade³

1978

The Journal of Cell Biology

133

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“…In any case chelator action has nothing to do with protection of sulfhydryl groups, which are necessary for the enzyme to be active [4,20]. This was proved by extensive inhibition of the activity by sulfhydryl agents (Hg2+, HMB) regardless the chelator presence in the incubation medium.…”

Section: Discussionmentioning

confidence: 85%

Differential Effects of Metal-Binding Agents on the D-GIucose-6-Phosphate Phosphohydrolase Activity of the Rat Liver

Konopka¹

1975

Enzyme

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The metal-binding agents (citrate, oxalate, bicarbonate, EDTA) exert dual effects on D-glucose-6-phosphate phosphohydrolase activity in the homogenate as well as in the subcellular fractions. The important differences of the effects are associated with the concentration of the chelator and with time of its addition. The small (appriopriate) concentrations of the metal-binding agents stimulate and stabilize the enzyme activity. However, chelators used in higher concentrations exert the inhibitory influence on the activity of glucose-6-phosphatase. Stimulation of the reaction was observed only if the chelator was added before the enzyme-substrate complex formation has been started. The formation of the ternary complex : the enzyme(metal)-chelator substrate exerting a protective influence on the active centre has been suggested. The hypothesis of a similar action of the metal-binding agents and P(1) on the glucose-6-phosphatase as a metaloproteid has been proposed.

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“…In the absence of ATP, concentrations of CoA and palmitic acid higher than 50 and 20 ,uM, respectively, were inhibitory by themselves ( Table 2). The inhibitory effect of CoA by itself at high concentrations was possibly due to the thiol group, as glutathione and other thiol compounds are known to inhibit microsomal G-6-Pase activity [30,31]. There have been several other previous reports of nonesterified fatty acids affecting G-6-Pase activity (e.g.…”

Section: Resultsmentioning

confidence: 98%

Fatty acyl-CoA esters inhibit glucose-6-phosphatase in rat liver microsomes

Fulceri

Gamberucci

Scott

et al. 1995

Biochemical Journal

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In native rat liver microsomes glucose 6-phosphatase activity is dependent not only on the activity of the glucose-6-phosphatase enzyme (which is lumenal) but also on the transport of glucose-6-phosphate, phosphate and glucose through the respective translocases T1, T2 and T3. By using enzymic assay techniques, palmitoyl-CoA or CoA was found to inhibit glucose-6-phosphatase activity in intact microsomes. The effect of CoA required ATP and fatty acids to form fatty acyl esters. Increasing concentrations (2-50 microM) of CoA (plus ATP and 20 microM added palmitic acid) or of palmitoyl-CoA progressively decreased glucose-6-phosphatase activity to 50% of the control value. The inhibition lowered the Vmax without significantly changing the Km. A non-hydrolysable analogue of palmitoyl-CoA also inhibited, demonstrating that binding of palmitoyl-CoA rather than hydrolysis produces the inhibition. Light-scattering measurements of osmotically induced changes in the size of rat liver microsomal vesicles pre-equilibrated in a low-osmolality buffer demonstrated that palmitoyl-CoA alone or CoA plus ATP and palmitic acid altered the microsomal permeability to glucose 6-phosphate, but not to glucose or phosphate, indicating that T1 is the site of palmitoyl-CoA binding and inhibition of glucose-6-phosphatase activity in native microsomes. The type of inhibition found suggests that liver microsomes may comprise vesicles heterogeneous with respect to glucose-6-phosphate translocase(s), i.e. sensitive or insensitive to fatty acid ester inhibition.

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Effects of sulfhydryl reagents on synthetic and hydrolytic activities of multifunctional glucose-6-phosphatase

Cited by 20 publications

References 20 publications

Endoplasmic reticulum marker enzymes in Golgi fractions--what does this mean?

Endoplasmic reticulum marker enzymes in Golgi fractions--what does this mean?

Differential Effects of Metal-Binding Agents on the D-GIucose-6-Phosphate Phosphohydrolase Activity of the Rat Liver

Fatty acyl-CoA esters inhibit glucose-6-phosphatase in rat liver microsomes

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