Pentose phosphate isomerase and epimerase from animal tissues

Dickens, F.; Williamson, Dermot H.

doi:10.1042/bj0640567

Cited by 80 publications

(22 citation statements)

References 34 publications

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“…They suggested that the phosphorylated 3-ketose was an intermediate in the interconversion of D-erythro-2-pentulose &phosphate and ~-threo-2-pentulose 5-phosphate. A similar intermediate was also detected by Dicltelis and Williamson while they were studying the same reaction using a rabbit muscle enzyme preparation (15).…”

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confidence: 67%

The Preparation of Erythro-3-Pentulose

Stoodley¹

1961

Can. J. Chem.

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confidence: 67%

The Preparation of Erythro-3-Pentulose

Stoodley¹

1961

Can. J. Chem.

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“…The combined rate of formation of all three hexose phosphates was only one-sixtieth of the initial rate of ribose 5-phosphate utilization. There have been numerous reports of various rates of ribose 5-phosphate utilization during the time course of its incubation with enzymes prepared from many tissues: erythrocyte haemolysates (Dische, 1951);higher plants (Axelrod et al, 1953); liver (Glock, 1952); acetone-dried powder enzyme preparations of muscle, erythrocytes and Krebs II carcinoma ascites cells (Dickens & Williamson, 1956). During the 17h time course of this study the relative amounts of ribose 5-phosphate, xylulose 5-phosphate and ribulose 5-phosphate (Table 4) were not maintained at 1978 equilibrium (Tabachnik et al, 1958), which would prevail if the activities of ribose phosphate isomerase and ribulose phosphate 3-epimerase were alone controlling the concentrations of these intermediates.…”

Section: Discussionmentioning

confidence: 99%

The fate of 14C in glucose 6-phosphate synthesized from [1-14C]Ribose 5-phosphate by enzymes of rat liver

Williams¹,

Clark²,

Blackmore³

1978

Biochemical Journal

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1. Glucose 5-phosphate was synthesized from ribose 5-phosphate by an enzyme extract prepared from an acetone-dried powder of rat liver. Three rates of ribose 5-phosphate utilization were observed during incubation for 17 h. An analysis of intermediates and products formed throughout the incubation revealed that as much as 20% of the substrate carbon could not be accounted for. 2. With [1-14C]ribose 5-phosphate as substrate, the specific radioactivity of [14C]glucose 6-phosphate formed was determined at 1, 2, 5 and 30 min and 3, 8 and 17 h. It increased rapidly to 1.9-fold the initial specific radioactivity of [1-14C]ribose 5-phosphate at 3 h and then decreased to a value approximately equal to that of the substrate at 6 h, and finally at 17 h reached a value 0.8-fold that of the initial substrate [1-14C]ribose 5-phosphate. 3. The specific radioactivity of [14C]ribose 5-phosphate decreased to approx. 50% of its inital value during the first 3 h of the incubation and thereafter remained unchanged. 4. The distribution of 14C in the six carbon atoms of [14C]glucose 6-phosphate formed from [1-14C]ribose 5-phosphate at 1, 2, 5 and 30 min and 3, 8 and 17 h was determined. The early time intervals (1--30 min) were characterized by large amounts of 14C in C-2 and in C-6 and with C-1 and C-3 being unlabelled. In contrast, the later time intervals (3--17 h) were characterized by the appearance of 14C in C-1 and C-3 and decreasing amounts of 14C in C-2 and C-6. 5. It is concluded that neither the currently accepted reaction sequence for the non-oxidative pentose phosphate pathway nor the 'defined' pentose phosphate-cycle mechanism can be reconciled with the labelling patterns observed in glucose 6-phosphate formed during the inital 3 h of the incubation.

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“…Detection was either by dipping the dried paper in aniline-phosphoric acid-acetic acid solution (cf. Dickens & Williamson, 1956b), or, for polyols and sugars having adjacent hydroxyls, by the periodic acid-benzidine reagent (Gordon, Thornburg & Werum, 1956). The presence of radioactive spots was detected by a thin-window Panex monitor (model 50A), and for semi-quantitative purposes counts were made on squares 2 cm.…”

Section: Methodsmentioning

confidence: 99%