Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The metabolism of 2-deoxy-D-galactose has been studied in AS-30D rat ascites hepatoma cells in suspension. Using 2-deoxy-D-(1-14C)galactose and an alkaline ethanol deproteinization procedure, the quantitatively identified metabolites included 2-deoxy-D-galactose 1-phosphate comprising 99.3%, and UDP-2-deoxy-D-galactose and UDP-2-deoxy-D-glucose, together amounting to 0.4% of the total metabolites. After incubation for 5 h in the presence of 2-deoxy-D-galactose (1 mmo1/1), the content of 2-deoxy-D-galactose 1-phosphate reached 35 mmo1x(kg cells)-1. The rate of phosphorylation of 2-deoxy-D-galactose was rapid during the first 30 min and decreased to approximately 20% of this rate during the subsequent hours. The rapid trapping of Pi in the form of 2-deoxy-D-galactose 1-phosphate resulted in a depression of free intracellular Pi in spite of a concomitant increase in net 32Pi uptake from the medium and a decrease of ATP and other 5'-nucleotides. The rates of glucose utilization and lactate production were depressed by more than 80% in the presence of 2-deoxy-D-galactose (1 mmo1/1). Interruption of Pi trapping by removal of 2-deoxy-D-galactose from the medium reversed the depressions of Pi and ATP and resulted in a rapid but incomplete relief of glycolysis inhibition. Crossover analysis of glycolytic intermediates indicated an inhibition at the 6-phosphofructokinase step. The depression of glucose utilization may be mediated by the increased level of glucose 6-phosphate, a potent inhibitor of hexokinase. An additional inhibitory effect of a metabolite of 2-deoxy-D-galactose at the 6-phosphofructokinase step was indicated by crossover analysis after reversal of Pi and ATP depressions in the presence of a high intracellular content of 2-deoxy-D-glactose 1-phosphate. The quantitative analysis of the metabolites of 2-deoxy-D-galactose demonstrated the predominance of the monophosphate and the negligible formation of UPD derivatives of this sugar analog in AS-30D hepatoma cells. This provides a system for the investigation of a galactose analog as a phosphate-trapping agent in the virtual absence of uridylate trapping.
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PMID:2-Deoxy-D-galactose metabolism in ascites hepatoma cells results in phosphate trapping and glycolysis inhibition. 19 12

A new procedure for separately isolating milligram quantities of rabbit renal proximal straight (PST) or convoluted (PCT) tubules is described, and the differential abilities of these segments to utilize glucose as a metabolic substrate are investigated. Separate dissection of the cortical cortices and the outer medullary stripe, followed by collagenase digestion and discontinuous Percoll centrifugation, provide enriched populations (greater than 98% pure) of PCT (37 mg) and PST (14 mg), respectively, per rabbit. The purity of PCT and PST fractions was quantitated morphologically and by comparing the enriched activity of the proximal tubular marker leucine aminopeptidase and deenriched activity of the distal marker hexokinase to previously published values reported from microdissection studies. To investigate glucose-dependent metabolic differences, PCT and PST suspensions (1 mg/ml) were preincubated in Dulbecco's modified Eagle's-Ham's F-12 medium for 1 h before being incubated for 30 min in buffer with or without glucose as the only available metabolic substrate. In glucose-containing buffer, PST segments maintained their oxygen consumption and ATP contents at levels significantly higher than PCT segments. These differential responses between PST and PCT were glucose-dependent because they were abolished when segments were incubated under glucose-free conditions. Because responses in PCT were glucose-independent, these results suggest that PCT cannot utilize glucose to support oxidative metabolism, whereas PST segments can oxidatively metabolize this substrate. These differences in glucose utilization do not correlate with the distribution of glycolytic enzyme activities, suggesting that differential metabolic regulation of these enzymes may determine the ability of each segment to utilize glucose.
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PMID:Bulk isolation of renal PCT and PST. I. Glucose-dependent metabolic differences. 237 89