Thiols of the Erythrocyte

Morell, Samuel A.; Ayers, Valborg E.; Greenwalt, Tibor J.; Hoffman, P.

doi:10.1016/s0021-9258(18)93907-4

Cited by 23 publications

(3 citation statements)

References 26 publications

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“…Electrophoresis conditions were as described in the text. (Morell et al, 1964). We found that both these compounds inhibited ketohexokinase, but that pchloromercuribenzoate was more effective at the same concentration.…”

Section: Physical Properties Of Ketohexokinasementioning

confidence: 67%

The purification and properties of human liver ketohexokinase. A role for ketohexokinase and fructose-bisphosphate aldolase in the metabolic production of oxalate from xylitol

Bais¹,

James²,

Rofe³

et al. 1985

Biochemical Journal

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Ketohexokinase (EC 2.7.1.3) was purified to homogeneity from human liver, and fructose-bisphosphate aldolase (EC 4.1.2.13) was partially purified from the same source. Ketohexokinase was shown, by column chromatography and polyacrylamide-gel electrophoresis, to be a dimer of Mr 75000. Inhibition studies with p-chloromercuribenzoate and N-ethylmaleimide indicate that ketohexokinase contains thiol groups, which are required for full activity. With D-xylulose as substrate, ketohexokinase and aldolase can catalyse a reaction sequence which forms glycolaldehyde, a known precursor of oxalate. The distribution of both enzymes in human tissues indicates that this reaction sequence occurs mainly in the liver, to a lesser extent in the kidney, and very little in heart, brain and muscle. The kinetic properties of ketohexokinase show that this enzyme can phosphorylate D-xylulose as readily as D-fructose, except that higher concentrations of D-xylulose are required. The kinetic properties of aldolase show that the enzyme has a higher affinity for D-xylulose 1-phosphate than for D-fructose 1-phosphate. These findings support a role for ketohexokinase and aldolase in the formation of glycolaldehyde. The effect of various metabolites on the activity of the two enzymes was tested to determine the conditions that favour the formation of glycolaldehyde from xylitol. The results indicate that few of these metabolites affect the activity of ketohexokinase, but that aldolase can be inhibited by several phosphorylated compounds. This work suggests that, although the formation of oxalate from xylitol is normally a minor pathway, under certain conditions of increased xylitol metabolism oxalate production can become significant and may result in oxalosis.

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Section: Physical Properties Of Ketohexokinasementioning

confidence: 67%

The purification and properties of human liver ketohexokinase. A role for ketohexokinase and fructose-bisphosphate aldolase in the metabolic production of oxalate from xylitol

Bais¹,

James²,

Rofe³

et al. 1985

Biochemical Journal

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“…The apparent rate constants of metHb reduction by thiols (k 1 app ) were measured by an absorbance increase at 430 nm in the Soret band (deoxyHb) during the incubation of the metHb solution (10 µM) with each thiol compound (20-60 mM) at 37 °C and pH 7.0 in 50 mM HEPES buffer. The apparent rate constants for thiol oxidation by oxygen (k 2 app ) during incubation of the thiol solution (15 mM) at an oxygen partial pressure (P O2 ) of 713 Torr at 37 °C and pH 7.0 in 50 mM HEPES buffer were calculated from the decrease in the amount of SH group quantitatively measured using an N-ethylmaleimide method (Morell et al, 1964).…”

Section: Methodsmentioning

confidence: 99%

Methemoglobin Formation in Hemoglobin Vesicles and Reduction by Encapsulated Thiols

et al. 1997

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The hemoglobin vesicle (HbV) is a red cell substitute encapsulating purified concentrated Hb in a phospholipid vesicle. In order to suppress metHb formation or autoxidation, for the long-term maintenance of the oxygen transporting capability, a series of thiols (cysteine, Cys; glutathione, GSH; homocysteine, Hcy; and acetylcysteine, Acy) were studied as reductants of metHb. Hcy and GSH showed a good suppressive effect on metHb formation, while Cys adversely accelerates the metHb formation at a rate twice that of the Hb solution without any reductants and Acy showed no change. The significant suppression by the coaddition of superoxide dismutase (SOD) and catalase to Cys indicated that Cys was easily oxidized by oxygen and simultaneously generates a large amount of active oxygens. The effective suppression of metHb formation by SOD and catalase was not observed for HbV containing no reductants, indicating that the generation of active oxygens from Hb itself is not significant. The coencapsulation of Hcy with Hb resulted in a low rate of metHb formation in HbV (initial rate, 1%/h) in vitro at an oxygen partial pressure (Po2) of 142 Torr. The rate increased with decreasing Po2, showed a maximum (2.2%/h) around Po2 = 23 Torr, and then decreased to 0%/h at 0 Torr. From these results, it is suggested that the fast metHb formation rate in the blood circulation of Wistar rats injected with 20 vol % of the HbV solution would be mainly caused by the exposure of HbV to the low Po2.

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“…The solution was sealed in a vial and bubbled with N 2 , and then preserved at 40 °C to accelerate decomposition. After 3 days and 1, 2, 3, and 4 weeks, the thiol group in Hcy was quantitatively measured using an N-ethylmaleimide method (Morell et al, 1964).…”

Section: Preparation Of Poly(ethylene Glycol) (Peg)-mentioning

confidence: 99%

Poly(ethylene glycol)-Conjugation and Deoxygenation Enable Long-Term Preservation of Hemoglobin-Vesicles as Oxygen Carriers in a Liquid State

et al. 2000

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The stability of hemoglobin vesicles (HbV) as an oxygen infusion was tested during the storage for 1 year at 4, 23, and 40 degrees C. The surface of the HbV was modified with poly(ethylene glycol) (PEG), and the suspension was deoxygenated with nitrogen bubbling. The samples stored at 4 and 23 degrees C showed a stable dispersion state for 1 year, though the sample stored at 40 degrees C showed the precipitation and decomposition of vesicular components, a decrease in pH, and 4% leakage of total Hb after 1 year. The PEG chains on the vesicular surface stabilize the dispersion state and prevent the aggregation and fusion due to their steric hindrance. The original metHb content (ca. 3%) before the preservation gradually decreased to less than 1% in all the samples after 1 month due to the presence of homocysteine inside the vesicles which consumed the residual oxygen and gradually reduced the trace amount of metHb. The rate of metHb formation was strongly dependent on the partial pressure of oxygen, and no increase in metHb formation was observed due to the intrinsic stability of the deoxygenated Hb. Preservation at 4 and 23 degrees C slightly reduced P(50) (increased the oxygen affinity) from 38 Torr to 32 and 31 Torr, respectively. These results indicate the possibility that HbV suspension can be stored at room temperature for at least 1 year.

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Thiols of the Erythrocyte

Cited by 23 publications

References 26 publications

The purification and properties of human liver ketohexokinase. A role for ketohexokinase and fructose-bisphosphate aldolase in the metabolic production of oxalate from xylitol

The purification and properties of human liver ketohexokinase. A role for ketohexokinase and fructose-bisphosphate aldolase in the metabolic production of oxalate from xylitol

Methemoglobin Formation in Hemoglobin Vesicles and Reduction by Encapsulated Thiols

Poly(ethylene glycol)-Conjugation and Deoxygenation Enable Long-Term Preservation of Hemoglobin-Vesicles as Oxygen Carriers in a Liquid State

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