Enzymes Of Glycogen Metabolism Research Articles

The Enzymes Of Glycogen Metabolism in the Various Cell Fractions from the Normal Human Epidermis

In the normal human epidermis, glycogen synthetase is sedimented with glycogen as is the glycogen synthetase D phosphatase which converts the D to the I form. Glycogen synthetase I kinase is not associated with glycogen. Phosphorylase is associated (sedimentable) with glycogen to a lesser extent and exists mainly in the b form. Phosphorylase b kinase is present in the normal human epidermis and it is not associated with glycogen under our experimental conditions.

Effects of denervation on the glycogen content and on the activities of enzymes of glucose and glycogen metabolism in rat diaphragm muscle.

1. Changes in the content and concentration of glycogen and in the activity of a number of enzymes involved in glucose and glycogen metabolism were studied in the rat hemidiaphragm after unilateral denervation. 2. After nerve section the tissue hypertrophies; this hypertrophy is said to be confined to the smaller red fibres and not to the white. 3. The total hexokinase activity increases, whereas that of total glycogen phosphorylase decreases. The specific activity of phosphorylase a, determined after Halothane anaesthesia, remains fairly constant. 4. In fed animals the denervated tissue stores less glycogen, but in the early stages its glycogen content does not fall on starvation. 5. The effect of denervation on the specific activities of several other characteristically white-fibre enzymes are not consistent with the response of glycogen phosphorylase; the increase in content of glyceraldehyde 3-phosphate dehydrogenase and lactate dehydrogenase is thought to be related to proliferation of the sarcoplasmic reticulum. 6. The ratio of lactate dehydrogenase M/H subunits increases at the height of the hypertrophy, but then declines as the mass of the tissue falls. 7. The chronology of these changes in enzyme activities suggests a multiplicity of distinct responses after nerve section not consistent with any one model, either specific fibre development or reversion to de-differentiated, foetal-type metabolism.

Occurrence of intramitochondrial glycogen in canine myocardium after prolonged anoxic cardiac arrest

Intramitochondrial glycogen deposits were observed in viable cardiac muscle cells of dogs sacrificed 2 to 4 weeks following prolonged periods of normothermic anoxic cardiac arrest induced by aortic cross-clamping during total cardiopulmonary bypass. These deposits were not observed in control dogs, in dogs which died several hours to 8 days after the anoxic period, or in cardiac biopsies taken immediately before and immediately after the anoxic period. The intramitochondrial glycogen deposits were located in the outer mitochondrial compartment, and varied from few to large numbers of granules that almost completely filled the mitochondria. These granules occurred in the monoparticulate (β) form and usually were slightly larger than the extramitochondrial β glycogen granules. Both intra- and extramitochondrial glycogen gave a strongly positive reaction with the periodic acid-thiosemicarbazide-silver proteinate method of Thiéry for the demonstration of polysaccharides; glycogen granules in both locations were extracted from ultrathin sections by amylase. Although intramitochondrial glycogen deposits have been described in a few patients with cardiomyopathies, the present study suggests that such deposits indicate a type of response to injury rather than a specific type of cardiomyopathy. It is suggested that the three factors responsible for the occurrence of intramitochondrial glycogen deposits in cardiac muscle cells following anoxic cardiac arrest are: (i) solubilization of the enzymes of glycogen metabolism during the anoxic period: (ii) increased permeability, due to anoxic damage, of the outer mitochondrial membrane; and (iii) diffusion of the solubilized enzymes of glycogen synthesis into the mitochondria with subsequent formation of glycogen.

Developmental Changes of Glycolytic and Gluconeogenic Enzymes in Fetal and Neonatal Rat Liver

In fetal and in neonatal rat liver the following enzymes of glycogen metabolism and of the upper part of the Embden-Meyerhof pathway and the pentose-phosphate-shunt were determined: G6Pase, F1,6DPase, G6PDH, 6PGDH, HK, F6PK, PGM, PGI, Phosphorylase, glycogen synthetase with and without G6P, and finally the lysosomal α-glucosidase.

Studies on the structure and metabolism of glycogen in some abnormal human infants.

1. The liver and muscle tissues of 14 human anencephalic babies were examined for glycogen content and structure, and for the activities of several glycogen-metabolizing enzymes. 2. In both tissues glycogen content increased with gestation age; the muscle glycogens had a slightly but significantly lower degree of branching than the corresponding liver glycogens. 3. All the expected glycogen-metabolizing enzymes were present; acid maltase activities were higher and phosphoglucomutase activities were lower than the results reported for human adult tissues. Glucose 6-phosphatase activity increased significantly with gestation age.

Effect of propylthiouracil feeding on glycogen metabolism and malic enzyme in the liver of the chick ( Gallus domesticus)

1. 1. A significant increase in liver glycogen took place 3 days after beginning the feeding of a diet containing propylthiouracil (PTU) while a significant increase in liver weight occurred after 4 days. 2. 2. Glucose-6-phosphatase was decreased after 3 days and malic enzyme after 5 days of feeding the PTU diet. 3. 3. Phosphorylase, phosphoglucomutase and glutamic oxaloacetic transaminase were higher in PTU-fed birds compared to control birds. 4. 4. There was a return to normal in all indices when PTU was removed from the diets of the chicks. Three enzymes changed away from the normal values temporarily before returning to normal. These changes were faster than the changes in the birds when PTU was introduced into the diet. 5. 5. A latent period of 24 hr was observed before the activities of phosphorylase, phosphoglucosamine and glucose-6-phosphatase showed indications of rising after the birds were returned to a PTU-free diet. 6. 6. Glucose-6-phosphatase seems to be the limiting enzyme in glycogenolysis in PTU-fed chicks.

Binding of enzymes of glycogen metabolism to glycogen in skeletal muscle

The distribution of glycogen synthetase, phosphorylase, and amylo-1,6-glucosidase in subcellular fractions was studied in human and rabbit skeletal muscle. All glycogen synthetase and 60–70% of phosphorylase and amylo-l,6-glucosidase were sedimented with the microsome-glycogen fraction. These enzymes were redistributed to the final supernatant when glycogen was either digested by glucamylase or metabolically utilized in vitro, and the process was reversed by the addition of glycogen. Redistribution of the enzymes to the final supernatant also followed depletion of glycogen by sustained tetanus in vivo. When glycogen was separated from microsomes by filtration, the enzymes passed through the filter with glycogen. These results suggest that the principal enzymes of glycogen synthesis and degradation are bound to the polysaccharide rather than to membranes of the sarcoplasmic reticulum.

Enzymes of glycogen metabolism in human skin with particular reference to differential diagnosis of the glycogen storage diseases.

1. A vacuum skin-blistering technique has been successfully applied and the human epidermal tissue so obtained has been examined for glycogen content and some of the enzymes involved in glycogen metabolism. 2. Normal values for glycogen phosphorylase, acid α-glucosidase and amylo-1,6-glucosidase (debranching enzyme) in epidermis are reported. Glucose 6-phosphatase activity was not detected. 3. Examination of two patients with Type II glycogen storage disease (Pompe's Disease—lack of lysosomal acid α-glucosidase) revealed an absence of the acid α-glucosidase in their skin. 4. The enzymic lesion in Type V glycogen storage disease (McArdle's Disease—lack of muscle phosphorylase) was not reflected in the epidermal tissue of a patient and a normal level of the enzyme was observed.

Control of Phosphorylase Activity in a Muscle Glycogen Particle: III. REGULATION OF PHOSPHORYLASE PHOSPHATASE

Abstract This study describes a new type of inhibition of phosphorylase phosphatase that strongly suggests that the activity of this enzyme is modulated during regulation of the phosphorylase system. Phosphorylase phosphatase included in a muscle protein-glycogen complex along with phosphorylase, phosphorylase kinase, and other enzymes of glycogen metabolism undergoes a reversible inhibition when phosphorylase is activated. This inhibition requires free Ca2+ in addition to Mg-ATP, i.e. the same conditions that trigger phosphorylase activation; it is observed only in the intact protein-glycogen complex. It is not caused by AMP or IMP generated from the rapid breakdown of ATP, two nucleotides known to inhibit the phosphorylase phosphatase reaction by binding to the substrate phosphorylase a. (a) Addition of AMP or IMP to the particulate system is without effect; (b) phosphatase activity returns to normal at the end of an activation cycle of phosphorylase when concentration of IMP is maximum; and (c) the same inhibition pattern is observed when a phosphopeptide derived from phosphorylase a is used as substrate, a reaction not affected by AMP or IMP. Digestion of glycogen in the complex by α-amylase abolishes the Ca2+-dependent inhibition of phosphorylase phosphatase, but the activity of this enzyme is still predominantly unaffected by nucleotides. On the other hand, dissociation of the protein-glycogen complex by dilution brings about both a loss of the Ca2+-dependent inhibition of the phosphatase and the reappearance of its sensitivity to AMP or IMP. Phosphorylase phosphatase included in the complex acts on phosphorylase a endogenously produced by addition of Ca2+, Mg2+, and ATP 16-fold faster than on soluble phosphorylase a added to the system. Nevertheless, the phosphatase reaction on the exogenous substrate still remains unaffected by high concentrations of AMP or IMP. No evidence was obtained that during inhibition the enzyme was covalently modified, e.g. by phosphorylation; rather, it is proposed that this inhibition results from the interaction of phosphorylase phosphatase with some of the other components of the phosphorylase system.

Properties of liver glycogen isolated in density gradients of sodium lothalamate

A technique is described for isolation of highly purified liver glycogen by centrifuging through density gradients of sodium iothalamate. Sodium iothalamate (the salt of 5-acetamido-2,4,6-triiodo- N-methylisophthalamic acid) in stock solution (80% w v ) has a density of 1.499 g/cc. Density varies linearly with refractive index providing a useful measure of density gradients. In gradients formed during prolonged ultracentrifugation, glycogen bands isopyenically at 1.46–1.48 g/cc. Using simple discontinuous gradients, glycogen from crude liver homogenates bands at the interface of iothalamate layers of 1.46 and 1.40 g/cc after 4-hr centrifugation at 40,000 rpm in a titanium 50 rotor. After removal of iothalamate by dialysis, the isolated glycogen retains its aggregate structure as shown by rate-zonal centrifugation in linear iothalamate density gradients from 1.12–1.28 g/cc. The purity of the product is shown by electron microscopy and spectrophotometry. The branched structure of the glycogen polymer was intact as determined by an absorption maximum of glycogen-iodine complexes at 480 mμ. The isolated product contains approximately 6% residual protein which may represent attached glycogen-metabolizing enzymes.

Glycogen, glycogen-metabolizing enzymes, and acid and alkaline phosphatases in the endometrium of the ewe during early pregnancy.

The concentration of glycogen and glucose and the activity of several glycogenmetabolizing enzymes have been measured in the endometrium of the ewe during early pregnancy and after the injection of progesterone and 20ex-hydroxypregn-4-en- 3-one. The activity of acid and alkaline phosphatases following the injection of steroids and the histochemical localization of the latter enzyme in the endometrium during early pregnancy have also been examined

The localization of glycogen in the spermatozoa of various invertebrate and vertebrate species.

With the periodic acid-thiosemicarbazide-silver proteinate procedure for the detection of polysaccharides in thin sections, glycogen is localized in the cavities of centrioles and basal bodies, within the axoneme (and surrounding it), in mitochondria, and in the "packing" cytoplasm of the middle piece of spermatozoa of several invertebrate and vertebrate species. The cytochemical localization of glycogen is verified by extraction with alpha-amylase solution. These findings establish the existence of stored glycogen in sperm. The polysaccharide presumably serves as an endogenous source of energy in the absence of extracellular metabolites, under either aerobic or anaerobic conditions. Other hypotheses on the physiological significance of intracellular glycogen stores in sperm are discussed. Sperm that store glycogen contain some enzymes of glycogen metabolism. In the presence of glucose-1-phosphate, ATP, and Mg(++) ions, an amylophosphorylase catalyzes the in vivo synthesis of glycogen. The newly formed product resembles gamma-particles, and is digestible with alpha-amylase.

Histochemical studies on the enzymes of glycogen metabolism in hamster epididymis.

Active and total (active + inactive) phosphorylase and glycogen synthetase (I- and D-form) were studied in hamster epididymis in relation to glycogen. Immature and adult, sexually active and regressed animals were examined.

Effect of insulin in vivo on diaphragm and adipose tissue of obese mice.

Effect of insulin in vivo on diaphragm and adipose tissue of obese mice.

Glycogen and glycogen-metabolizing enzymes in the squirrel monkey uterine cervix

The uterine cervical squamous stratified epithelium of squirrel monkeys (Saimiri sciurea) was studied for localization of glycogen, phosphorylases, glycogen synthetase, and branching enzyme, 2 weeks after ovariectomy, with and without subsequent treatment with physiologic and hyperphysiologic levels of estradiol benzoate. All the above substances were virtually absent 2 weeks following ovariectomy and did not reappear unless the animals were sufficiently stimulated with estrogen to give the full histologic response of proliferation and cornification. In responding animals there was a tendency for glycogen and enzymes to be located close to the cervical squamocolumnar junction and to diminish toward the ectocervix. Following 3 months' continuous treatment with a very large dose of estrogen, small amounts of glycogen and of phosphorylase activity were observed in the epithelium, but glycogen synthetase and branching enzyme could not be demonstrated.

Enzymes of glycogen metabolism in cerebral cortex of normal and diabetic rats.

Enzymes of glycogen metabolism in cerebral cortex of normal and diabetic rats.

Enzymes of glycogen metabolism in the squamous epithelium of the cervix. A histochemical study.

Enzymes of glycogen metabolism in the squamous epithelium of the cervix. A histochemical study.

Enzymes of glycogen metabolism in white blood cells. 3. Heterogeneity of glycogen phosphorylase from rat chloroma.

Summary 1. Glycogen phosphorylase ( α -1,4-glucan:orthophosphate glucosyltransferase (EC 2.4.1.1)) of rat chloroma has been purified and partially characterized. 2. Column chromatography on o -(diethylaminoethyl)-cellulose yields 2 phosphorylase peaks both of which are active without adenosine 5′-phosphate. The identity of these 2 peaks has been ascertained by rechromatography on O -(diethylaminoethyl)-cellulose and electrophoresis on acrylamide gel. 3. There appears to be some distinct differences in the properties of the enzyme from the 2 peaks. 4. The finding of 2 isoenzymes of phosphorylase in rat chloroma represents the second example of heterogeneity of this enzyme, the first example being that of phosphorylase from rabbit heart.

Phosphorylase and Related Enzymes of Glycogen Metabolism

Publisher Summary The finding that pyridoxal phosphate is an essential constituent or coenzyme of glycogen phosphorylase created a new dimension for thought concerning the functions of vitamin B6. This chapter explores questions, such as “Did the discovery of vitamin B6 in phosphorylase stimulate avenues of approach that have led to new disclosures concerning functions of vitamin B6? Have any of the classical findings of vitamin B6 deficiency been explained as a consequence of impaired phosphorylase activity?” The chapter reviews the progress that has been made in several laboratories as to the mechanism of action of pyridoxal phosphate in phosphorylase. In view of the complex role of phosphorylase in the regulation of glycogen metabolism, the chapter focuses on the phosphorylase system. The interconversion reactions of the two forms of phosphorylase catalyzed by phosphorylase b kinase and phosphorylase phosphatase are briefly reviewed. The chapter evaluates the role of vitamin B6 in carbohydrate metabolism in general.

The Activity of Some Enzymes of Glycogen Metabolism in Fetal and Neonatal Guinea Pig Liver

The Activity of Some Enzymes of Glycogen Metabolism in Fetal and Neonatal Guinea Pig Liver