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PubMed1993

Alterations in brain hexokinase activity associated with heart failure in rats.

This study examined the activity of discrete regions of the brain as assessed with histological localization and photodensitometric quantification of the metabolic enzyme hexokinase in a group of rats with coronary occlusion (HF) and in sham-operated control rats. Three weeks after surgery, the mean left ventricular end diastolic pressure and right atrial pressure were elevated, and left ventricular peak systolic pressure was decreased in the HF group compared with the sham group; these findings are also observed during heart failure. In addition, histological data indicated that there was a 37.6 +/- 2.8% outer and 40.8 +/- 3.1% inner infarct of the myocardium in the group of rats with HF (n = 6). Rats in the control group had no observable damage to the myocardium (n = 6). Accompanying these symptoms of heart failure were significant increases in hexokinase activity in the parvocellular (pPVN, 16.3%) and magnocellular (mPVN, 17.6%) divisions of the paraventricular nucleus of the hypothalamus, and in the locus ceruleus (LC, 17.1%). No changes in hexokinase activity were observed in the median preoptic area, supraoptic nucleus (SON), subfornical organ, or posterior hypothalamus. These results reinforce the idea that heart failure (with coronary occlusion) is associated with changes in specific areas in the brain and that metabolic alterations in the pPVN, mPVN, and LC are likely related to alterations in vasopressin production, blood volume regulation, and sympathoexcitation observed in the heart failure state.

Animals↗
PubMed1981

Distribution of hexokinase and phosphoenolpyruvate carboxykinase along the rabbit nephron.

Radiochemical microprocedures were developed for the determination of hexokinase and phosphoenolpyruvate carboxykinase (PEPCK) activity in single microdissected segments of the mature rabbit nephron dissected from fresh tissue after collagenase treatment. All results were related to tubular length and tubular protein content. Hexokinase activity was found to be lowest in the proximal convoluted tubule and to increase along the following nephron segments, with highest activity in the connecting tubule. The gluconeogenic enzyme PEPCK, on the other hand, was exclusively found in the proximal tubule. Early and late portions of the convoluted segment exhibited the same specific activity, but only 50% was found in the pars recta. All other renal structures exhibited only insignificant activity of PEPCK. The results show that renal glucose metabolism and gluconeogenesis are clearly separated. As previously shown for the cytosolic rat enzyme, rabbit mitochondrial PEPCK is also exclusively a proximal tubular enzyme, thus confirming the dominant role of this segment in mammalian renal gluconeogenesis. The high activity of hexokinase in the segments of the distal tubule points to the role of glucose as metabolic fuel, glycogen precursor, and other glucose-6-phosphate-using pathways in these structures.

Animals↗
PubMed1999

Chronic activation of 5'-AMP-activated protein kinase increases GLUT-4, hexokinase, and glycogen in muscle.

This study was designed to determine whether chronic chemical activation of AMP-activated protein kinase (AMPK) would increase glucose transporter GLUT-4 and hexokinase in muscles similarly to periodic elevation of AMPK that accompanies endurance exercise training. The adenosine analog, 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), has previously been shown to be taken up by cells and phosphorylated to form a compound (5-aminoimidazole-4-carboxamide ribonucleotide) that mimics the effect of AMP on AMPK. A single injection of AICAR resulted in a marked increase in AMPK in epitrochlearis and gastrocnemius/plantaris muscles 60 min later. When rats were injected with AICAR (1 mg/g body wt) for 5 days in succession and were killed 1 day after the last injection, GLUT-4 was increased by 100% in epitrochlearis muscle and by 60% in gastrocnemius muscle in response to AICAR. Hexokinase was also increased approximately 2. 5-fold in the gastrocnemius/plantaris. Gastrocnemius glycogen content was twofold higher in AICAR-treated rats than in controls. Chronic chemical activation of AMPK, therefore, results in increases in GLUT-4 protein, hexokinase activity, and glycogen, similarly to those induced by endurance training.

Aminoimidazole Carboxamide↗
PubMed1984

Red blood cell hexokinase in Fanconi's anemia.

The activity of ten red blood cell enzymes, including hexokinase, has been measured in 6 Fanconi's anemia patients. In disagreement with previous reports, in no instance were reduced or increased hexokinase levels found. Furthermore, the hexokinase isozymic pattern, thermostability, pH dependence of activity and kinetic properties were also in the normal range.

Adolescent↗
PubMed1983

Red blood cell hexokinase in tumor bearing mice.

Red blood cell hexokinase of tumor-bearing BALB/c mice was found to be 35% higher than in the normal controls, whereas glucose 6-phosphate-dehydrogenase and other red blood cell glycolytic enzymes were in the normal range. This hexokinase increase cannot be explained by a mean younger red cell population because normal hematological data and normal red cell enzymes, known as red cell age-markers, have been found in tumor-bearing mice. The isozymic pattern of red cell hexokinase is not modified in the tumor-bearing mice.

Animals↗
PubMed1982

Reciprocal distribution of hexokinase and glucokinase in the periportal and perivenous zone of the rat liver acinus.

Glucokinase and hexokinase activities were measured in the periportal and perivenous zone of the liver acinus separated by microdissection. A microfluorimetric assay was established for the separate determination of both enzyme activities. Glucokinase activity was about 3.5-fold higher in the perivenous than in the periportal zone in fed male and female rats. after 24 h starvation this gradient was only slightly changed. Hexokinase showed an inverse gradient with about 1.5-fold higher activities in the periportal than in the perivenous zone in both fed and fasted animals. Since glucokinase is restricted to parenchymal cells and hexokinase is present predominantly or even exclusively in non-parenchymal cells, the heterogeneous distribution of glucokinase activity supports the model of a "metabolic zonation of liver parenchyma" with a predominance of glucose uptake in the perivenous and glucose release in the periportal hepatocytes.

Animals↗
PubMed1993

The effects of hyperinsulinemia and hyperglycemia on GLUT4 and hexokinase II mRNA and protein in rat skeletal muscle and adipose tissue.

The GLUT4 glucose transporter and type II hexokinase are predominantly expressed in skeletal muscle and adipose tissue. The effects of insulin and glucose on the expression of GLUT4 and HKII were studied in vivo by using the euglycemic-hyperinsulinemic and hyperglycemic-hyperinsulinemic clamp methods. The clamps were maintained in conscious rats for 6 or 24 h after a 1-day starvation period. Adipose tissue GLUT4 mRNA was increased 4-fold after 6 h and 23-fold after 24 h of hyperinsulinemia; HKII mRNA was increased by four- and eightfold after 6 and 24 h, respectively. In contrast, GLUT4 mRNA was not significantly changed in skeletal muscle by either the euglycemic- or hyperglycemic-hyperinsulinemic clamps. Each of these treatments resulted in a fourfold induction of HKII mRNA. No changes of GLUT4 protein and hexokinase activity were detected after 6 h of hyperinsulinemia in either skeletal muscle or adipose tissue. After 24 h of hyperinsulinemia, adipose tissue GLUT4 protein had doubled, whereas skeletal muscle GLUT4 was unchanged. In contrast, hexokinase activity increased by two- to eightfold in skeletal muscle and adipose tissue. Hyperinsulinemia alone was sufficient to mediate the effects observed, because no additional effects were seen when hyperglycemia accompanied hyperinsulinemia. These results reveal the lack of coordinate regulation of GLUT4 and HKII in adipose tissue and skeletal muscle. Whereas hyperinsulinemia increases both GLUT4 and HKII mRNA and protein levels in adipose tissue, this treatment increases HKII mRNA and protein in skeletal muscle, but has no effect on GLUT4 in this tissue.

Adipose Tissue↗
PubMed1994

Molecular model of human beta-cell glucokinase built by analogy to the crystal structure of yeast hexokinase B.

Recent studies have shown that mutations in human beta-cell glucokinase that impair the activity of this key regulatory enzyme of glycolysis can cause early-onset non-insulin-dependent diabetes mellitus (NIDDM). The amino acid sequence of human glucokinase has 31% identity with yeast hexokinase, a related enzyme for which the crystal structure has been determined. This homology has allowed us to model the three-dimensional structure of human glucokinase by analogy to the crystal structure of yeast hexokinase B. This model of human glucokinase provides a basis for understanding the effects of mutations on its enzymatic activity. Residues in the active site and on the surface of the binding cleft for glucose are highly conserved in both enzymes. Regions far from the active site are predicted to differ in conformation, and 10 insertions or deletions that range in size from 1 to 7 residues are located on the protein surface between elements of secondary structure. The model structure suggests that human glucokinase binds glucose in a similar manner to yeast hexokinase. The glucose-binding site contains a conserved aspartic acid, two conserved glutamic acids, and two conserved asparagines that form hydrogen bond interactions with the hydroxyls of the glucose similar to those observed in other sugar-binding proteins. Mutation of residues in the predicted glucose-binding site has been found to greatly reduce enzymatic activity. This model will be useful for future structure/function studies of glucokinase.

Amino Acid Sequence↗
PubMed2000

Effects of D-mannoheptose and D-glycero-D-gulo-heptose upon D-glucose metabolism and insulinotropic action in rat pancreatic islets and D-glucose phosphorylation by hexokinase isoenzymes: comparison with D-mannoheptulose.

The possible use of D-mannoheptose or D-glycero-D-gulo-heptose as substitute of D-mannoheptulose for specific inhibition of D-glucose phosphorylation, metabolism and insulinotropic action was investigated in the present study. The two aldoheptoses failed to duplicate the effect of D-mannoheptulose upon the phosphorylation of D-glucose by yeast hexokinase, bovine heart hexokinase or human B-cell glucokinase. They were poorly phosphorylated by the low-Km hexokinase isoenzymes or liver B-cell glucokinase. D-mannoheptose failed to reproduce the inhibitory action of D-mannoheptulose upon D-glucose metabolism by isolated rat pancreatic islets. Whilst D-glycero-D-gulo-heptose failed to affect glucose-induced insulin release, D-mannoheptose slightly enhanced glucose-induced insulin release when tested at low concentrations (0.75-1.5 mM) and progressively decreased insulin output at higher concentration (3. 0-20.0 mM) in islets exposed to a high (16.7 mM), but not physiological (8.3 mM), concentration of D-glucose. D-mannoheptose, however, also caused a modest inhibition of insulin release evoked by 2-ketoisocaproate. It is concluded, therefore, that neither D-mannoheptose nor D-glycero-D-guloheptose can be considered as suitable substitutes of D-mannoheptulose.

Animals↗
PubMed2001

D-mannoheptulose phosphorylation by hexokinase isoenzymes.

D-mannoheptulose is a specific inhibitor of D-glucose phosphorylation by hexokinase isoenzymes. In the present study, the phosphorylation of this heptose was investigated by either a spectrophotometric or radioisotopic procedure. Using yeast hexokinase, the phosphorylation of 25 mM D-mannoheptulose only represented 0.02% of that of 5 mM D-glucose. Such a percentage was increased to 3.93% in the case of bovine heart hexokinase. In the latter case, the Km for D-mannoheptulose was close to 0.2 mM and both D-glucose (0.1-1.0 mM) and D-glucose 6-phosphate (also 0.1-1.0 mM) inhibited the phosphorylation of the heptose (0.03-0.60 mM). Human B-cell glucokinase also catalyzed the phosphorylation of D-mannoheptulose (0.1 mM), which was now increased in a bell-shaped manner by D-glucose (1.0-20 mM). Likewise, rat parotid gland, liver and pancreatic islet homogenates catalyzed the phosphorylation of D-[3H]mannoheptulose. The results obtained in these three tissues differed from one another by their absolute values (per mg wet wt.), relative values (by reference to the phosphorylation rate of 10 mM D-glucose), and sensitivity to inhibition by D-glucose (10 mM).

Amino Acid Substitution↗
PubMed1999

Studies of gene expression and activity of hexokinase, phosphofructokinase and glycogen synthase in human skeletal muscle in states of altered insulin-stimulated glucose metabolism.

When whole body insulin-stimulated glucose disposal rate is measured in man applying the euglycaemic, hyperinsulinaemic clamp technique it has been shown that approximately 75% of glucose is taken up by skeletal muscle. After the initial transport step, glucose is rapidly phosphorylated to glucose-6-phosphate and routed into the major pathways of either glucose storage as glycogen or the glycolytic/tricarboxylic acid pathway. Glucose uptake in skeletal muscle involves-the activity of specific glucose transporters and hexokinases, whereas, phosphofructokinase and glycogen synthase hold critical roles in glucose oxidation/glycolysis and glucose storage, respectively. Glucose transporters and glycogen synthase activities are directly and acutely stimulated by insulin whereas the activities of hexokinases and phosphofructokinase may primarily be allosterically regulated. The aim of the review is to discuss our present knowledge of the activities and gene expression of hexokinase II (HKII), phosphofructokinase (PFK) and glycogen synthase (GS) in human skeletal muscle in states of altered insulin-stimulated glucose metabolism. My own experimental studies have comprised patients with disorders characterized by insulin resistance like non-insulin-dependent diabetes mellitus (NIDDM) and insulin-dependent diabetes mellitus (IDDM) before and after therapeutic interventions, patients with microvascular angina and patients with severe insulin resistant diabetes mellitus and congenital muscle fiber type disproportion myopathy as well as athletes who are in a state of improved insulin sensitivity. By applying the glucose insulin clamp method in combination with nuclear magnetic resonance 31P spectroscopy to normoglycaemic or hyperglycaemic insulin resistant subjects impairment of insulin-stimulated glucose transport and/or phosphorylation in skeletal muscle has been shown. In states characterized by insulin resistance but normoglycaemia, the activity of HKII measured in needle revealed any genetic variability that contributes to explain the decreased muscle levels of GS mRNA or the decreased activity and activation of muscle GS in NIDDM patients and their glucose tolerant but insulin resistant relatives. Thus, the causes of impaired insulin-stimulated glycogen synthesis of skeletal muscle in normoglycaemic insulin resistant subjects are likely to be found in the insulin signalling network proximal to the GS protein. In insulin resistant diabetic patients the impact of these yet unknown abnormalities may be accentuated by the prevailing hyperglycaemia and hyperlipidaemia. Endurance training in young healthy subjects results in improved insulin-stimulated glucose disposal rates, predominantly due to an increased glycogen synthesis rate in muscle, which is paralleled by an increased total GS activity, increased GS mRNA levels and enhanced insulin-stimulated activation of GS. These changes are probably due to local contraction-dependent mechanisms. Likewise, one-legged exercise training has been reported to increase the basal concentration of muscle GS mRNA in NIDDM patients to a level similar to that seen in control subjects although insulin-stimulated glucose disposal rates remain reduced in NIDDM patients. In the insulin resistant states examined so far, basal and insulin-stimulated glucose oxidation rate at the whole body level and PFK activity in muscle are normal. In parallel, no changes have been found in skeletal muscle levels of PFK mRNA and immunoreactive protein in NIDDM or IDDM patients. In endurance trained subjects insulin-stimulated whole body glucose oxidation rate is often increased. However, depending on the intensity and frequency, physical exercise may induce an increased, a decreased or an unaltered level of muscle PFK activity. In athletes the muscle PFK mRNA is similar to what is found in sedentary subjects whereas the immunoreactive PFK protein concentration is decreased.

Animals↗
PubMedDate not supplied

[Activity and isoenzymatic makeup of the hexokinase of rapid and slow muscles in the rabbit normally and the experimental allergic polyneuritis].

An activity and isozyme spectrum of hexokinase were studied in rapid (gastrocnemius) and slow (soleus) muscles of rabbit in normal state and in experimental allergic polyneuritis, caused by administration of myelin from peripheric nerves mixed with Freund's stimulator. In normal organism the hexokinase activity was shown to be several times higher in soleus muscle than in gastrocnemius one. In these muscles the isozyme spectrum of the enzyme was markedly differentiated. In gastrocnemius muscle of rabbits with experimental allergic polyneuritis the hexokinase activity was distinctly increased due to increase in amount of the II type of the enzyme; in soleus muscle the decrease in the total activity of the enzyme depended upon the decrease in amount ofhexokinase II.

Animals↗
PubMed1999

Structure-function analysis of yeast hexokinase: structural requirements for triggering cAMP signalling and catabolite repression.

In baker's yeast (Saccharomyces cerevisiae) the hexokinases PI (Hxk1) and PII (Hxk2) are required for triggering of the activation of the Ras-cAMP pathway and catabolite repression. Specifically, Hxk2 is essential for the establishment of glucose repression, whereas either Hxk1 or Hxk2 can sustain fructose repression. Previous studies have suggested that the extent of glucose repression is inversely correlated with hexokinase catalytic activity and hence with an adequate elevation of intracellular sugar phosphate levels. However, several lines of evidence indicate that glucose 6-phosphate is not the trigger of catabolite repression in yeast. In the present study we employed site-directed mutagenesis of amino acids important for the binding of sugar and ATP, for efficient phosphoryl transfer and for the closure of the substrate-binding cleft, to obtain an insight into the structural requirements of Hxk2 for sugar-induced signalling. We show that the ATP-binding Lys-111 is not essential for catalysis in vivo or for signal triggering. Substitution of the catalytic-centre Asp-211 caused loss of catalytic activity, but high-affinity sugar binding was retained. However, this was not sufficient to cause cAMP activation nor catabolite repression. Mutation of Ser-158 abrogated glucose-induced, but not fructose-induced, repression. Moreover, 2-deoxyglucose sustained repression despite an extremely low catalytic activity. We conclude that the establishment of catabolite repression is dependent on the onset of the phosphoryl transfer reaction on hexokinase and is probably related to the stable formation of a transition intermediate and concomitant conformational changes within the enzyme. In contrast, the role of Hxk2 in Ras-cAMP activation seems to be directly connected to its catalytic function. The implications of this model are discussed.

Amino Acid Sequence↗
PubMed1975

Effect of N6-(delta2-isopentenyl)adenosine treatment in vivo on hexokinase activity of mouse L 1210 cells.

The kinetic properties of hexokinase of L1210 ascites tumor cells propagated in DBA/2HaD mice are altered by treatment of the mice with the modified nucleoside N6-(delta2-isopentenyl)-adensone (IPA). Relative to animals not treated with IPA, ascites cell hexokinase showed an increased affinity for ATP and a decreased affinity for glucose as a result of IPA treatment. The heat stability of the enzyme was different in treated and untreated mice. It was concluded that IPA treatment may either produce changes in enzyme conformation which resulted in a change in control mechanisms or may induce the formation of a hexokinase isoenzyme.

Adenosine↗
PubMed1975

Identity, release, and binding of mitochondrial-bound hexokinases in mammary glands and adenocarcinomas of lactating mice.

The mitochondrial-bound hexokinases (adenosine triphosphate:D-hexose 6-phosphotransferase) of mammary adenocarcinoma and of normal gland were compared in lactating C3H mice. Treatment of mitochondria isolated from both the normal and neoplastic tissue with 0.5 m NaCl or 0.1 mM glucose 0-phosphate effected the release of about 50% of the bound hexokinase. In the presence of magnesium ion, enzyme from either source attached to mitochondria from either tissue and in all combinations to the same extent. Identification of the isoenzyme complement in the mitochondrial extract by diethylaminoethylcellulose chromatography revealed only types I and II. In the tumor, the hexokinase activity in both the cytosol and the fraction solubilized from mitochondria was predominantly in the form of type I ( 60%). In contrast, the activity released from mitochondria isolated from normal gland was predominately type II, while the cytosol contained almost equivalent amounts of types I and II. While this difference does not explain differences in glucose utilization between the normal and neoplastic tissue, it may provide a means of distinguishing between the two.

Animals↗
PubMed1976

pH-dependent effects of Cr(NH3)2ATP on kinetics of yeast hexokinase PII. Relationship to the slow transition mechanism.

The effect of Cr(NH3)2ATP, a virtually inert, inner sphere metal-ligand complex, on the kinetics of purified yeast hexokinase PII has been studied at pH 6.5 and pH 7.5. At pH 6.5, where the normal assays exhibit a slow burst-type transient, low concentrations of Cr(NH3)2ATP were found to activate both phii, the initial velocity, and phiII, the steady state velocity. At higher concentrations, Cr(NH3)2ATP was found to be a competitive inhibitor versus MgATP for both phii and phiII. The apparent Ki values for both velocities were the same. The inhibition by Cr(NH3)2ATP at pH 6.5 was found to be a slow process with half-times similar to those found for the normal burst-type transient at this pH value. At pH 7.5, where normal assays exhibit linear progress curves, Cr(NH3)2ATP behaved similarly to that observed before at pH 7 (Danenberg, D. D., and Cleland, W. W. (1975) Biochemistry 14, 28-39), i.e. it was a competitive inhibitor versus MgATP and it caused a slowing of the reaction rate over the first several minutes. The apparent Ki for the initial velocity was 8-fold higher than the apparent Ki for the steady state velocity, suggesting tighter binding of Cr(NH3)2ATP with time. Preincubation experiments indicated that the normal pH 6.5 burst-type transient could be eliminated by appropriate preincubation with Cr(NH3)2ATP and a sugar. In agreement with Danenberg and Cleland (1975), similar preincubations have been shown to produce linear assays at pH 7.5 in the presence of Cr(NH3)2ATP. Similar results were seen with MgITP as the nucleotide substrate, where a burst-type transient is not seen at either pH value under normal assay conditions. At pH 7.5, a slow decrease in the reaction rate is seen over the first several minutes in the presence of Cr(NH3)2ATP. The apparent Ki for phii was 7-fold higher than the apparent Ki value for phiII, again suggesting a tighter binding of Cr(NH3)2ATP with time. A similar observation was made at pH 6.5, but the Ki values for phii and phiII were the same, suggesting no tightening of the binding of Cr(NH3)2ATP with time at this pH value. These results suggested that both slow processes reflect the same basic molecular change, but the consequences are different at the two pH values, presumably because of the difference in the charge of the enzyme. The Cr(NH3)2ATP kinetics at pH 6.5 have been interpreted in terms of a modification of the slow transition mechanism for hexokinase (Shill, J. P., and Neet, K. E. (1975) J. Biol. Chem. 250, 2259-2268). It is postulated that glucose and Cr(NH3)2ATP induce the same slow conformational change at pH 6.5 as that induced by glucose and MgATP, which gives rise to the normal burst-type transient. This suggests that Cr(NH3)2ATP may be a useful tool for physical studies to determine the cause of the slow transition of yeast hexokinase. Activation by low concentrations of Cr(NH3)2ATP was interpreted as binding of the nucleotide to an activator site on the enzyme, causing a shift in the distribution of enzyme towards the more active form.

Adenosine Triphosphate↗
PubMed2005

Nitric oxide stimulates 18F-FDG uptake in human endothelial cells through increased hexokinase activity and GLUT1 expression.

UNLABELLED: The endothelium constitutes a functionally active organ critically involved in angiogenesis. Nitric oxide (NO) is an important regulator of vascular homeostasis and angiogenesis and stimulates glucose metabolism in certain cells. We thus investigated the effect of exogenous NO on (18)F-FDG transport in human endothelial cells. METHODS: Human umbilical vein endothelial cells (HUVECs) were treated with the NO donors sodium nitroprusside (SNP) or diethylenetriamine (DETA), in concentrations of 1 micromol/L-1 mmol/L for up to 24 h. (18)F-FDG uptake levels corrected for protein content were determined by cellular radioactivity measured after 30-min incubation. Cells were evaluated for total hexokinase activity and plasma membrane glucose transporter 1 (GLUT1) levels, and involvement of potential signaling pathways was investigated by cotreatment with respective protein kinase inhibitors. RESULTS: Both SNP and DETA stimulated HUVEC (18)F-FDG uptake, which began at 16 h and peaked at 24 h. The increase in (18)F-FDG uptake was dose dependent, reaching 464.0% +/- 49.8% and 254.5% +/- 10.8% of control levels at 24 h with 1 mmol/L SNP and DETA, respectively. Exposure of HUVECs to 1 mmol/L SNP resulted in a 3.5 +/- 0.3-fold elevation in hexokinase activity (P < 0.01) and a significant increase in GLUT1 levels. SNP-stimulated (18)F-FDG uptake was abolished by cotreatment with cycloheximide, the tyrosine kinase inhibitor genistein, the phosphatidylinositol-3 kinase (PI3K) inhibitor wortmannin, or the protein kinase C inhibitor staurosporine. CONCLUSION: NO stimulates (18)F-FDG uptake in HUVECs through an increase in GLUT1 expression and hexokinase activity, which appears to involve both protein kinase C and PI3K pathways.

Cells, Cultured↗
PubMedDate not supplied

[Liver hexokinase isoenzymes in carcinogenesis].

Four isoenzymes of hexokinase were isolated by means of chromatography on DEAE-cellulose from soluble fraction of Vistar rat liver tissue. One of the isoenzymes (IV) was a glucokinase. Four fractions were also found in starch gel electrophoresis. These fractions catalyzed phosphorylation of glucose. Besides alterations in the total activity of hexokinase the changes in isoenzyme spectra were observed in carcinogenesis, caused by diethyl nitrosoamine. In the course of development of the blastomatose process in liver tissue content of isoenzymes I, II and, especially, of III was increased, and content of isoenzyme IV was decreased. In tissue of primary hepatomas, induced by diethyl nitrosoamine, the isoenzyme spectra of hexokinase did not significantly differ from the spectra of the enzyme in liver tissue at later stages of carcinogenesis.

Animals↗