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

1. Procedures were developed for the extraction and assay of glycolytic enzymes from the epididymis and epididymal spermatozoa of the rat. 2. The epididymis was separated into four segments for analysis. When rendered free of spermatozoa by efferent duct ligation, regional differences in enzyme activity were apparent. Phosphofructokinase, glycerol phosphate dehydrogenase and glucose 6-phosphate dehydrogenase were more active in the proximal regions of the epididymis, whereas hexokinase, lactate dehydrogenase and phosphorylase were more active in the distal segment. These enzymes were less active in the epididymis of castrated animals and less difference was apparent between the proximal and distal segments. However, the corpus epididymidis from castrated rats had lower activities of almost all enzymes compared with other epididymal segments. 3. Spermatozoa required sonication to obtain satisfactory enzyme release. Glycolytic enzymes were more active in spermatozoa than in epididymal tissue, being more than 10 times as active in the case of hexokinase, phosphoglycerate kinase and phosphoglycerate mutase. 4. The specific activities of a number of enzymes in the epididymis were dependent on the androgen status of the animal. These included hexokinase, phosphofructokinase, aldolase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase, pyruvate kinase, glycerol phosphate dehydrogenase, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and phosphorylase. 5. The caput and cauda epididymidis differed in the extent to which enzyme activities changed in response to an altered androgen status. The most notable examples were hexokinase, phosphofructokinase, aldolase, phosphoglycerate kinase, 6-phosphogluconate dehydrogenase and phosphorylase.
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PMID:Activity and androgenic control of glycolytic enzymes in the epididymis and epididymal spermatozoa of the rat. 18 56

Various enzymes of glycolysis (hexokinase, phosphoglucoisomerase, aldolase and lactate dehydrogenase), the Krebs cycle (isocitrate, succinic and malate dehydrogenases), and the pentose phosphate cycle (glucose-6-phosphate and 6-phosphogluconate dehydrogenases) were studied in buffalo spermatozoa by biochemical and cytochemical methods. The enzymes of glycolysis were found to be loosely bound whereas those of the Krebs and pentose phosphate cycles were strongly bound to mitochondrial membranes. All the enzymes studied were localized histochemically in the mid-piece.
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PMID:Glycolytic, Krebs cycle and pentose phosphate cycle enzymes in spermatozoa of the buffalo (Bubalus bubalis). 51 3

Microdetermination methods were used to determine the activities of hexokinase in human and mouse oocytes, human spermatozoa, and other somatic cells. Human oocytes with intact germinal vesicle obtained from the growing follicle were freeze dried and weighed (mean +/- SD = 243 +/- 34 ng dry weight). Hexokinase activity in single oocytes was 17.9 +/- 3.6 pmol of reduced nicotinamide-adenine dinucleotide phosphate formed/oocyte/hr at 20 degrees C. Specific activity was estimated to be 104 +/- 30 nmol/mg protein/hr, which was remarkably lower than that in human spermatozoa (3570 +/- 550 nmol/mg protein/hr) and other somatic cells such as endometrium, brain, liver, and kidney. Mouse follicular oocytes and early embryos before the two-cell stage also had low hexokinase activities, but morulae and blastocysts had increasingly high activities; the former cannot use glucose as an energy source, whereas the latter can. These results suggest that human immature oocytes, as well as mouse oocytes, depend on pyruvate instead of glucose as a major energy source.
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PMID:Studies of hexokinase activity in human and mouse oocyte. 233 32

The regulation of oxidative phosphorylation was studied with digitonin-treated epididymal bull spermatozoa in which mitochondria are directly accessible to low molecular compounds in the extracellular medium. Due to the high extramitochondrial ATPase activity in this cell preparation, it was possible to stimulate respiration to a small extent only by added hexokinase in the presence of glucose and adenine nucleotides. Added pyruvate kinase plus phosphoenol pyruvate, however, strongly suppressed the respiration. Under these conditions, the respiration was found to depend on the extramitochondrial [ATP]/[ADP] ratio in the range of 1-100. The contribution of the adenine nucleotide translocator to this dependence was determined by titration with the irreversible inhibitor carboxyatractyloside in the presence of ADP. Using lactate plus malate as substrate, the active state respiration was controlled to about 30% by the translocator, whereas 12 and 4% were determined in the presence of L-glycerol-3-phosphate and malate alone, respectively. In order to compare the results with those for intact cells, the adenine nucleotide patterns were determined in intact and digitonin-treated spermatozoa under conditions of controlled respiration in the presence of vanadate and carboxyatractyloside, respectively. About 21% of total cellular adenine nucleotides were found in digitonin-treated cells representing the mitochondrial compartment. While allowing for the intramitochondrial amount of adenine nucleotides, the cytosolic [ATP]/[ADP] ratio was estimated to be 6-times higher than the mitochondrial ratio in intact cells. It is concluded from the data presented that the principal mechanism by which oxidative phosphorylation in sperm mitochondria is regulated via the extramitochondrial [ATP]/[ADP] ratio is the same as that demonstrated for other isolated mitochondria.
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PMID:Regulation of oxidative phosphorylation in mitochondria of epididymal bull spermatozoa. 360 41

The Michaelis-Menten constants (Km) of glucose, fructose, galactose, 2-deoxy-D-glucose and ATP as substrate for hexokinase of spermatocyte, spermatid and cauda epididymal spermatozoa extracts were measured. The Km value of glucose was very similar for all three germ cells. It was also true for all other substrates. The affinity of glucose for this enzyme was the highest while that of fructose was the lowest. The Km values were in general agreement with characteristics of hexokinase extracted from other tissues of rat. The Vmax values were also determined. The Vmax ratio of fructose to glucose showed the highest values of 1.1. The Vmax ratios of other substrates to glucose were below 1.0. The results suggest that hexokinase in the germ cells is similar to that in other tissues in its kinetic properties.
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PMID:Kinetic properties of hexokinase of germ cells in rat testis. 381 51

1. Methods of homogenizing suspensions of washed mammalian spermatozoa were studied. The most useful methods were those using sonication and those using a French press. 2. Hexokinase, phosphofructokinase, glucose phosphate isomerase and adenosine triphosphatase activities in ram, bull and boar spermatozoa were investigated by using these two homogenization methods. Glucose phosphate isomerase, representative of soluble cytoplasmic material, was very readily extracted and remained entirely in the supernatant after centrifugation at 145000g for 60min. In contrast, the other three activities were less easily extracted and were sedimented in various proportions under the described conditions of centrifugation. 3. Attempts to obtain subcellular fractions from sperm homogenates by ;classical' methods failed, owing apparently to the inhomogeneity of subcellular particles in the homogenates. It is concluded that, after removal of sperm heads, the only meaningful fractionation is a separation of spermatozoal material which sediments at 145000g during 60min from that which does not. 4. The stabilities of hexokinase and phosphofructokinase activities in bull, boar and ram sperm homogenates were investigated. Hexokinases showed very little dependence on the various environments tested, whereas the optimum conditions for phosphofructokinase stability were: a minimum of sonication, the presence of phosphate ions and of a thiol-group protectant, and a pH7.5. Activities of hexokinase, phosphofructokinase and glucose phosphate isomerase per sperm cell were compared with published data on rates of fructolysis by spermatozoa; the potential catalytic activities were shown to be considerably in excess of these rates. However, phosphofructokinase may be the rate-limiting enzyme of glycolysis in vivo in bull and ram spermatozoa.
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PMID:Glycolytic enzymes in mammalian spermatozoa. Activities and stabilities of hexokinase and phosphofructokinase in various fractions from sperm homogenates. 425 94

The effect of adrenalectomy and corticosterone replacement on epididymal enzymes involved in obligatory steps of glycolysis and pentose phosphate pathway were studied along with serum hormonal profiles. Adrenalectomy was found to elevate serum prolactin while the gonadotropins and testosterone were unaltered. In caput epididymal tissue enzymes of the pentose phosphate pathway. Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities were increased after adrenalectomy. However, in corpus epididymal tissue the key enzymes viz. hexokinase, 6-phosphofructokinase and pyruvatekinase of the glycolytic pathway were elevated leaving the pentose phosphate pathway unaffected. Adrenalectomy was also found to favour glycolysis of the epididymal spermatozoa. The possible direct effect of prolactin is discussed to explain the enzymatic changes in epididymis. Corticosterone replacement was found to maintain the enzyme activities along with serum prolactin and corticosterone at control levels. In conclusion, it is suggested that the adrenalectomy induced changes in enzyme activities could be due to the direct effect of prolactin.
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PMID:Effect of adrenalectomy and corticosterone replacement on epididymal carbohydrate metabolism--studies on mature male rats. 640 94

Assay of maximal activities of 11 glycolytic enzymes in cell-free buffalo sperm extracts showed that hexokinase, phosphofructokinase and glyceraldehyde-3-phosphate dehydrogenase had the lowest activities, suggesting regulation of fructolysis at steps catalysed by these enzymes. The ratios of glyceraldehyde-3-phosphate dehydrogenase/phosphofructokinase (0.67) and phosphoglycerate kinase/phosphofructokinase (4.60) are typical of cells exhibiting high Pasteur effect (50% for ejaculated buffalo spermatozoa). The regulatory nature of phosphofructokinase was shown through its modulation by ATP, AMP and inorganic phosphate. The determination of fructolytic intermediates and cofactors and calculation of mass action ratios for each enzymic step revealed that hexokinase, phosphofructokinase, fructose-biphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase and pyruvate kinase catalysed reactions far removed from the equilibrium. A regulatory role by glyceraldehyde-3-phosphate dehydrogenase appeared to be most likely because triosephosphates and inorganic phosphate accumulated more under anaerobic than under aerobic conditions.
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PMID:REgulation of glycolysis/fructolysis in buffalo spermatozoa. 645 53

Washing of bull and ram spermatozoa resulted in significant losses of lactic dehydrogenase (LDH) and glucose phosphate isomerase (GPI) from the cell suspensions. Re-suspension of washed bull spermatozoa caused an immediate release of enzymes from the cells. Preincubation of washed ram spermatozoa with 0.025% formaldehyde increased GPI levels but decreased LDH concentration in the extracellular fluid while hexokinase release was unaffected. Varying the incubation temperature between 20 and 37 degrees C affected extracellular LDH and GPI levels. It is suggested that enzyme release from spermatozoa may occur in the absence of any apparent cellular damage.
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PMID:Studies on leakage of enzymes from washed bull and ram spermatozoa. 701 29

The chlortetracycline fluorescence assay was used to study the status of capacitation and the extent of induced acrosome reactions in cauda epididymidal spermatozoa from fertile and infertile rats fed, respectively, with vehicle or ornidazole (400 mg kg-1 day-1) for 10 days. Uniform bright fluorescence over the whole head was classified as the uncapacitated pattern, whereas a postacrosomal dark band, and a uniformly weaker fluorescence over the acrosome, reflected patterns intermediate between the uncapacitated and acrosome-reacted states. Acrosome-reacted spermatozoa displayed a dark head but always retained fluorescence at their tip. There was no difference between experimental and control groups of rats with regard to the development of the chlortetracycline fluorescence patterns during incubation. Under basal incubation conditions, the acrosome reaction was slightly delayed in spermatozoa from ornidazole-treated animals. In contrast, more spermatozoa were acrosome reacted in this group after incubation for 5 h when the concentration of BSA was increased from 4 to 20 mg ml-1. The Ca(2+)-ionophore A23187 induced a similar stimulation of capacitation and acrosome reactions in spermatozoa from control and ornidazole-fed animals, but in the latter group A23187 caused strong immobilization of spermatozoa. In the capacitation medium containing 5 mmol lactate l-1 and 5 mmol glucose l-1, the straight-line velocity of spermatozoa from ornidazole-treated rats was reduced by 50% compared with controls, irrespective of the concentration of BSA. Two glycolytic enzymes, triose phosphate isomerase and glyceraldehyde 3-phosphate dehydrogenase, displayed reduced activity (48% and 68% of controls, respectively) in cauda epididymidal spermatozoa from ornidazole-fed rats, whereas the activities of hexokinase and lactate dehydrogenase remained unchanged. This finding suggests that the fertility-compromising action of ornidazole is due to a disturbed glycolytic pathway.
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PMID:Influence of oral administration of ornidazole on capacitation and the activity of some glycolytic enzymes of rat spermatozoa. 869 6


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