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PubMed1980

Effects of acute variation of fetal glycemia on glycogen storage and on glycogen synthase and phosphorylase activities in the liver of the rat fetus.

The effects of variations of glycemia from 1.7 to 35 mM on the activity of glycogen synthase and phosphorylase, on glycogen content, and on U-14C-glucose incorporation into glycogen in the liver of the near-term rat fetus were investigated. Hypoglycemia did not affect the activities of phosphorylase and synthase; total glycogen content was not modified, but incorporation of labeled glucose was markedly decreased. This is consistent with a decreased glycogen synthesis. A slight hyperglycemia (about 5.5 mM) sharply decreased phosphorylase a (active) activity but increased slightly glycogen synthase a activity; liver glycogen content and labeled glucose incorporation were both enhanced. Higher levels of glycemia induced a decrease of phosphorylase a activity of the same order, but by contrast, glycogen synthase a activity increased progressively with increasing glycemia. Sequential study showed that hyperglycemia first induced the decrease of phosphorylase activity, then increased synthase activity. Marked hyperglycemia strongly enhanced liver glycogen content and labeled glucose incorporation. The fetal liver appears very responsive to acute variations of glycemia. The mechanisms seem to be oriented toward maximal glycogen accumulation.

Animals↗
PubMed1999

Synthesis and kinetic evaluation of 4-deoxymaltopentaose and 4-deoxymaltohexaose as inhibitors of muscle and potato alpha-glucan phosphorylases.

alpha-Glucan phosphorylases degrade linear or branched oligosaccharides via a glycosyl transfer reaction, occurring with retention of configuration, to generate alpha-glucose-1-phosphate (G1P). We report here the chemoenzymic synthesis of two incompetent oligosaccharide substrate analogues, 4-deoxymaltohexaose (4DG6) and 4-deoxymaltopentaose (4DG5), for use in probing this mechanism. A kinetic analysis of the interactions of 4DG5 and 4DG6 with both muscle and potato phosphorylases was completed to provide insight into the nature of the binding mode of oligosaccharide to phosphorylase. The 4-deoxy-oligosaccharides bind competitively with maltopentaose and non-competitively with respect to orthophosphate or G1P in each case, indicating binding in the oligosaccharide binding site. Further, 4DG5 and 4DG6 were found to bind to potato and muscle phosphorylases some 10-40-fold tighter than does maltopentaose. Similar increases in affinity as a consequence of 4-deoxygenation were observed previously for the binding of polymeric glycogen analogues to rabbit muscle phosphorylase [Withers (1990) Carbohydr. Res. 196, 61-73].

Animals↗
PubMedDate not supplied

[Effect of acetylcholine on phosphorylase from skeletal muscle].

Acetylcholine (1-10(-5) g/ml) was shown to increase the content of active form of phosphorylase A in homogenate of cat skeletal muscle. Atropine (1-10(-5) g/ml) diminished acetylcholine-induced increase in the phosphorylase activity from 22% to 5.28%. Activating effect of acetylcholine was observed also in superatant (105000 g), although it was 2-fold decreased. No acetylcholine-induced phosphorylase activation was observed in the presence of Mg2+. Addition of Ca2+ (2.2-10(-14) M) did not affect considerably the activation process. It is concluded that the mechanism of acetylcholine-induced phosphorylase activation is different from the effect of adrenaline on phosphorylase.

Acetylcholine↗
PubMed1992

High and intermediate affinity calmodulin binding domains of the alpha and beta subunits of phosphorylase kinase and their potential role in phosphorylation-dependent activation of the holoenzyme.

Phosphorylase kinase is a calcium-regulated multimeric enzyme of composition (alpha beta gamma delta)4, which contains calmodulin as the integral delta subunit and also is activated further by addition of extrinsic calmodulin. Previous studies by Dasgupta, M., Honeycutt, T., and Blumenthal, D.K. ((1989) J. Biol. Chem. 264, 17156-17163) have identified gamma 302-326 and gamma 342-366 as two calmodulin binding regions. Using peptides that were synthesized based on alpha and beta primary structure and that were predicted to contain the basic amphiphilic alpha-helix motif thought important for calmodulin binding, four additional potential calmodulin binding domains have now been identified: one of high affinity, beta 770-794; two of intermediate affinity, beta 5-28 and beta 920-946; and one with marginally low affinity, alpha 1070-1093. Peptide beta 770-794 was of higher calmodulin affinity than either gamma 302-326 or gamma 342-366; it was of higher affinity than the model synthetic peptide IV defined by O'Neil, K.T., and DeGrado, W.F. ((1990) Trends Biochem. Sci. 15, 59-64); and it is currently the most potent calmodulin-binding peptide so far described. Correlated with their affinity for calmodulin, all six phosphorylase kinase-derived peptides and several other established calmodulin-binding peptides inhibited phosphorylase kinase previously activated by cAMP-dependent phosphorylation, reducing its activity to the level of the nonactivated enzyme. However, these peptides did not inhibit (and some peptides slightly activated) the nonphosphorylated enzyme. Even in the presence of these peptides both activated and nonactivated enzyme remained fully Ca(2+)-dependent. The beta 770-794 peptide has at least a 5-fold greater calmodulin binding affinity than the holo-phosphorylase kinase. This, and its higher affinity for calmodulin than either of the sites on the gamma subunit, raises the possibility that in the native enzyme it may be involved in binding the intrinsic delta subunit. Further, inhibition of activated but not nonactivated enzyme by calmodulin-binding peptides would suggest that the phosphorylation-dependent activation of phosphorylase kinase may be mediated by changes in the binding interactions of the intrinsic calmodulin delta subunit.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2006

Evaluation of tumor angiogenesis and thymidine phosphorylase tissue expression in patients with endometrial cancer.

The formation of new blood vessels in endometrial cancer tissue is a main process, which leads to tumor progression, and is connected with tumor expansion and invasiveness. The aim of the study was evaluation of thymidine phosphorylase protein (TP) expression in human endometrial cancer cells by immunohistochemistry and comparison obtained data with intensity of angiogenesis process and clinicopathological factors as FIGO stage of disease and histopathologic grade. Endometrial cancer specimens were obtained from 55 postmenopausal patients (aged 52 to 74 years) underwent total abdominal hysterectomy with bilateral salpingo-oophorectomy. None of patients received preoperative pelvic irradiation. Histopathological typing and grading of the endometrial tumors (G-1, G-2, G-3) as well as myometrial invasion (<1/2, >1/2) were assessed using standard criteria, on hematoxylin-eosin sections. At the surgery, FIGO clinical stage of disease was determined. Thymidine phosphorylase overexpression was observed in 23 of 55 (41.8%) cases of endometrial cancer. Although we found no statistically significant differences in TP expression between histopathologic grades, particular FIGO stages showed a significant trend of increase TP tumor overexpression. Thymidine phosphorylase overexpression cases demonstrate higher intensity of angiogenesis in comparison to negative samples and results are statistically significant for t-test (p<0.0001). The most intensive new blood vessel formation was observed in G-2 of tumor differentiation grade (p=0.013 for ANOVA test) Mean angiogenic points density (APD) values in cases of G-1 histopathologic grade reached 135.7; values of G-2 and G-3 grades reached 213.8 and 162.8, respectively. Mean intensity of angiogenesis in the first FIGO stage of disease reached 160.0 APD, in stage II 205.6 APD, and in the third 286.9, respectively. Angiogenesis was more intensive in cases of advanced tumors - analysis of variance (ANOVA) confirmed statistically significant differences in APD values between FIGO stage groups (p=0.0007). In conclusion, thymidine phosphorylase expression correlates with increased microvessel density in endometrial cancer. The intensity of angiogenesis process increases according to FIGO stage of disease, which is connected with progressing of cancer disease. Thymidine phosphorylase can play an important role in endometrial cancer progression and could offer additional information about advance of disease.

Aged↗
PubMed1977

Effect of Mg2+ concentration on the cAMP-dependent protein kinase-catalyzed activation of rabbit skeletal muscle phosphorylase kinase.

Phosphorylase kinase was found to be activated and phosphorylated at 10mM Mg2+ by the cAMP-dependent protein kinase-catalyzed reaction ot much higher levels than observed previously when reactions were carried out in 1 to 2 mM Mg2+ (Cohen, P. (1973) Eur. J. Biochem. 34, 1; Hayakawa, T., Perkin, J.P., and Krebs, E.G. (1973) Biochemistry 12, 574). That the reaction at 10 mM Mg2+ is protein kinase-catalyzed is supported by several observations: (a) the reaction is facilitated by the addition of protein kinase; (b) the reaction depends on cAMP when protein kinase holoenzyme is uded; (c) the reaction is not inhibited by 1 mM ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetate which is known to inhibit autoactivation and autophosphorylation of phosphorylase kinase; and (d) the protein inhibitor of protein kinase inhibits this reaction. The phosphorylation and activation of phosphorylase kinase seem to occur in two phases. At low Mg2+ only the first phase is manifested and involves the incorporation of 2 mol of phosphate, 1 mol into each of Subunits A and B. At high Mg2+ additional sites are phosphorylated almost exclusively on Subunit A, with phosphate incorporation approaching the final level of 7 to 9 mol. Enzyme activity at high Mg2+ is 2 to 3 times higher than that observed when activation is studied at low Mg2+. The observation that both casein and type II histone are phosphorylated to the same extent at 1 mM and 10 mM Mg2+ suggested that high Mg2+ may be altering the conformation of phosphorylase kinase thus rendering more phosphorylation sites accessible to protein kinase. Since the phosphorylation of phosphorylase kinase by either the protein kinase-catalyzed or autocatalytic reaction can result in the incorporation of 7 to 9 mol of phosphate, the finding that only about seven sites become phosphorylated by both mechanisms acting together suggest that activation by these two mechanisms may involve common phosphorylation sites.

Animals↗
PubMed1990

Effect of host feeding and available glucose on glycogen synthase and phosphorylase activities in Hymenolepis diminuta and Vampirolepis microstoma.

The influences of host feeding and the availability of glucose in vitro on the activities of glycogen synthase and glycogen phosphorylase in Hymenolepis diminuta and in Vampirolepis microstoma were studied. The worms were recovered from hosts that had been fed ad libitum, starved for 24 hr, or starved 24 hr and then refed for 1 hr immediately prior to worm recovery. The ratios of active to inactive glycogen synthase and phosphorylase were correlated with the host feeding regimen prior to recovery. Glycogen synthase in H. diminuta was predominately in the inactive D form in worms from both fed and fasted hosts. One hour after refeeding, up to 80% of the synthase was in the active I form. Phosphorylase in H. diminuta was predominantly in the active a form in worms from fed and fasted hosts, but activity of this enzyme was suppressed in worms from refed hosts. When H. diminuta from fasted hosts was incubated in a balanced salt solution containing 40 mM glucose, glycogen synthase I increased, and phosphorylase a decreased. Glycogen synthase in V. microstoma was predominantly in the inactive D form in worms from both the fed and fasted hosts, but the proportion in the active I form increased to over half the total synthase by 1 hr of host refeeding. The proportion of glycogen phosphorylase a was high in worms from fed hosts and decreased, but not dramatically, in worms from fasted hosts. The results suggested that the worms had access to another source of glucose, probably from the host bile, and we measured a low but significant concentration of carbohydrate in the gall bladder bile of mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1978

Inactivation of phosphorylase phosphatase by a factor from rabbit liver and its chemical characterization as glutathione disulfide.

A factor inactivating phosphorylase phosphatase was isolated from rabbit liver. The isolation procedure consisted of heat treatment at 85 degrees C, extraction with n-butyl alcohol, and chromatography on Dowex 1 and DEAE-cellulose columns. The purified factor was different from the known protein inhibitors and was shown to be tripeptide composed of equimolar amounts of glutamic acid, cysteine, and glycine. The NH2-terminal and COOH-terminal amino acids were determined as glutamic acid and glycine, respectively. The factor was finally identified as glutathione disulfide by high voltage paper electrophoresis, paper chromatography, and liquid column chromatography using an amino acid analyzer. Addition of the purified factor or glutathione disulfide converted phosphorylase phosphatase to a stable, less active enzyme species, the extent of conversion depending on the amount added. The inactivated phosphatase was completely reactivated by addition of both glutathione (or 2-mercaptoethanol) and Mn2+ and partially reactivated by adding glutathione alone. Injection of glutathione disulfide into the portal vein of rabbits caused a rapid increase in phosphorylase alpha activity in the liver. These results suggest that glutathione disulfide is involved in regulation of phosphorylase activity in vivo, by causing inactivation of phosphorylase phosphatase in the liver.

Animals↗
PubMed1989

[Phosphorylation of isolated components of the troponin complex of skeletal and cardiac muscle phosphorylase kinase from bird skeletal muscles].

Pigeon and chicken skeletal muscle phosphorylase kinase purified to a nearly homogeneous state is able to phosphorylate both cardiac and skeletal troponin I and T. After 1-hr incubation, the enzyme transfers up to 0.35 mole of phosphorus per mole of skeletal troponin I, up to 0.5 mole of cardiac troponin I and up to 0.1 mole of cardiac and skeletal troponin T. Avian muscle phosphorylase kinase does not phosphorylate the first serine residue of cardiac and skeletal troponin T, but catalyzes the phosphate incorporation into the site(s) of troponin T located in the central or C-terminal parts of the protein molecule. The rate of troponin phosphorylation by pigeon muscle phosphorylase kinase is pH-dependent: the 6.8/8.2 ratio for troponin I is close to 0,2, whereas that with troponin T varies in the range of 0.5-0.7. Troponin phosphorylation by avian phosphorylase kinase depends on the presence of Ca2+ in the incubation mixture. In the presence of 3 mM EGTA troponin I phosphorylation is inhibited by 70-90%, whereas that of troponin T--by 50%. The experimental results indicate that the phosphorylation of troponin I and T is catalyzed either by two different active centers or by different conformations of the single center of avian phosphorylase kinase.

Animals↗
PubMed1989

[Purification, quaternary structure and regulatory properties of phosphorylase kinase from pigeon skeletal muscle].

Using DEAE-Toyopearl column chromatography, a preparation of pigeon skeletal muscle phosphorylase kinase was obtained in a state approaching homogeneity. The molecular mass of the native enzyme (1320 kDa) and the subunit formula (alpha beta gamma delta)4 are similar to those of rabbit and chicken counterparts. Both red and white pigeon skeletal muscle isozymes contain the alpha'-subunit instead of alpha. Gradient SDS-PAGE electrophoresis revealed small but well-reproducible differences in the molecular masses of rabbit, chicken and pigeon muscle beta- and gamma-subunits. The activity ratio at pH 6.8/8.2 is 0.06-0.15 for different preparations of phosphorylase kinase b. The activity of pigeon muscle phosphorylase kinase b is Ca2+-dependent. The [Ca2+]0.5 value at pH 7.0 is 20 microM, which exceeds that for the chicken muscle enzyme by two orders of magnitude. In the presence of Ca2+, pigeon phosphorylase kinase b is activated 4-fold by saturating concentrations of calmodulin and troponin C. Pigeon muscle phosphorylase b is activated 3-5-fold during autophosphorylation or phosphorylation by the catalytic subunit of cAMP-dependent protein kinase.

Animals↗
PubMed1987

Acyclonucleoside analogues consisting of 5- and 5,6-substituted uracils and different acyclic chains: inhibitory properties vs purified E. coli uridine phosphorylase.

Synthetic procedures are described for the preparation of a variety of pyrimidine acyclonucleoside analogues, in which the aglycones are 5- and 5,6-substituted uracils, and the ribose moiety is replaced by different acyclic chains. These were examined as potential inhibitors of purified E. coli uridine phosphorylase. None of the compounds was a substrate for uridine phosphorylase, or either a substrate or inhibitor of E. coli thymidine phosphorylase. Kinetic measurements were employed to determine inhibition constants, Ki, for inhibition of uridine phosphorylase. One of the more effective of these was 1-(1',3'-dihydroxy-2'-propoxy)methyl-5,6-tetramethyleneuracil, with Ki = 2.7 microM. The same compound was a reasonably good inhibitor of the reverse, synthetic, reaction, with Ki values of 19 microM vs uracil as the variable substrate, and 15 microM vs alpha-D-ribose-1-phosphate as the variable substrate. For one of the analogues, which was a racemate, 1-(2',3'-dihydroxypropyl)-5,6-tetramethyleneuracil, it was shown that only one of the enantiomers (R) was an inhibitor, the (S) enantiomer being totally inactive. For several of the analogues, the corresponding isomeric N(3)-acyclonucleosides were inactive as inhibitors. The results for several of the good inhibitors were compared with those of other observers for inhibition of uridine phosphorylase from mammalian sources. Preliminary measurements with several of our analogues demonstrated that some of them were indeed one to two orders of magnitude more effective against the enzyme from mammalian sources.

Escherichia coli↗
PubMed1985

Phosphorylase phosphatase catalytic subunit. Evidence that the Mr = 33,000 enzyme fragment is derived from a native protein of Mr = 70,000.

An active form of phosphorylase phosphatase of Mr = 33,000, referred to as the catalytic subunit for over a decade, was purified to near-homogeneity from rabbit skeletal muscle. Repeated immunization of a sheep produced immunoglobulins that blocked the activity of the phosphatase. These immunoglobulins were affinity-purified on columns of immobilized phosphorylase phosphatase and used as macromolecular probes in a "Western" immunoblotting procedure with peroxidase-conjugated rabbit anti-sheep immunoglobulins. Only one protein, of Mr = 33,000, was stained in samples of the immunogen, attesting to the specificity of the probes. However, the Mr = 33,000 phosphatase protein was not detected in muscle extracts or in partially purified preparations. Instead, a single protein of Mr = 70,000 was detected. Limited proteolysis, in particular by Staphylococcus aureus V8 protease and thermolysin, converted the immunoreactive protein from Mr = 70,000 to Mr = 33,000. Coagulation of the phosphatase preparation with 80% ethanol at room temperature rendered the Mr = 70,000 protein insoluble, but allowed extraction of the Mr = 33,000 protein from the precipitate. Thus, we conclude that the immunoreactive protein of Mr = 70,000 is the "catalytic subunit" of phosphorylase phosphatase with a catalytic domain of Mr = 33,000. Previous purification schemes have yielded only the fragment of Mr = 33,000 due to its relative resistance to proteolysis and coagulation. Gel filtration chromatography of the "native" form of phosphorylase phosphatase showed Mr approximately 230,000. Both the Mr = 70,000 catalytic subunit and a Mr = 60,000 protein related to inhibitor-2 were detected by immunoblotting in the same fractions that exhibited activity after treatment with Co2+ and trypsin. Only the Mr = 60,000 protein was degraded during this activation process. We propose that the native phosphorylase phosphatase is an elongated structure with two-fold symmetry, containing one catalytic subunit of Mr = 70,000 and one regulatory subunit of Mr = 60,000.

Animals↗
PubMed1985

The relationships between receptor binding capacity for norepinephrine, angiotensin II, and vasopressin and release of inositol trisphosphate, Ca2+ mobilization, and phosphorylase activation in rat liver.

Concentration-response relationships for norepinephrine-, angiotensin II-, and vasopressin-stimulated changes in cell Ca2+ content, phosphorylase activation, and cytosolic free Ca2+ and myo-inositol-P3 levels were examined in isolated hepatocytes. The specific binding of radioligands to alpha 1-adrenergic, vasopressin, and angiotensin II receptors was also examined in rat liver plasma membranes. Disparities occurred between the concentration-response curves for myo-inositol-P3 formation and the Ca2+ and phosphorylase responses, with the greatest difference being observed with vasopressin and the smallest with norepinephrine. It was also observed that all three agonists produced the same maximum changes in phosphorylase, cell Ca2+, and cytosolic Ca2+, but the maximum capacity of each agonist to generate myo-inositol-P3 varied greatly and was correlated with the maximum receptor binding capacity. The data indicated that a very small and submaximal elevation of myo-inositol-P3 was sufficient to maximally elevate cytosolic Ca2+ and activate phosphorylase. In addition, the relationship between the accumulation of myo-inositol-P3 and the elevation of cytosolic Ca2+ was similar, irrespective of whether the agonist was norepinephrine, angiotensin II, or vasopressin. It is proposed that the large differences between the concentration-response curves for myo-inositol-P3 formation and Ca2+ and phosphorylase changes observed with vasopressin and angiotensin II are due to the higher density of their receptors on liver cell plasma membranes compared with alpha 1-adrenergic receptors.

Angiotensin II↗
PubMed1988

Alpha-glucan phosphorylase from Escherichia coli. Cloning of the gene, and purification and characterization of the protein.

By using a synthetic oligonucleotide probe identical to a part of the gene for the Escherichia coli major outer membrane lipoprotein, we have cloned a gene from E. coli chromosomal DNA. However, the cloned gene was not one of the lipoprotein genes. The amino acid sequence deduced from its nucleotide sequence shows extensive similarities instead to alpha-glucan phosphorylase (EC 2.4.1.1). The gene, glgP, is located immediately downstream from glgA, the gene for glycogen synthase. The glgP gene was inserted into pUC9 vector and expressed in the presence of the lac inducer. The gene product was purified to apparent homogeneity as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In all chromatographies, the protein was eluted accompanied by a low phosphorylase activity. The final preparation showed phosphorolytic activity to various alpha-glucans, although the specific activity was extremely low compared to other alpha-glucan phosphorylases under the standard assay conditions. Its enzymatic activity, however, increased almost linearly as the concentration of glucan increased, reaching a value comparable with those of other phosphorylases. The amino acid sequence deduced was compared with those of alpha-glucan phosphorylases from other sources.

Amino Acid Sequence↗
PubMed1988

The abundance of calmodulin mRNAs is regulated in phosphorylase kinase-deficient skeletal muscle.

In the I/Lyn mouse strain a mutation on the X chromosome results in a deficiency of the major calmodulin-regulated enzyme in skeletal muscle, phosphorylase kinase. Calmodulin has been identified as the delta-subunit of phosphorylase kinase, and it is estimated that approximately 40% of the total calmodulin in rabbit skeletal muscle is associated with the phosphorylase kinase hexadecamer (alpha, beta, gamma, delta)4. The absence of phosphorylase kinase in I/Lyn skeletal muscle results in a reduction in the total amount of calmodulin. The mechanisms affecting this reduction were investigated by comparing the abundance and heterogeneities in calmodulin mRNAs between normal and phosphorylase kinase-deficient skeletal muscles. The results demonstrate that in normal tissue there are four species of calmodulin mRNA distinguished by their molecular weight. All four of these species are present in the deficient tissue, and none of them are preferentially reduced. However, there is a 54% reduction in all four mRNAs as well as in calmodulin in the deficient skeletal muscle relative to normal skeletal muscle. These results indicate that the expression of calmodulin mRNAs is coordinated with the expression of its major enzyme target in skeletal muscle.

Amino Acid Sequence↗
PubMed1987

[Interaction of muscle glycogen phosphorylase B with methotrexate, folic and folinic acids].

The interaction of rabbit skeletal muscle glycogen phosphorylase b with methotrexate, folic and folinic acids has been studied. Microscopic dissociation constant for the glycogen phosphorylase b--methotrexate complex determined by analytical ultracentrifugation is 0.43 mM. A subunit of glycogen phosphorylase b is shown to have two sites for methotrexate binding. AMP and FMN diminish the affinity of glycogen phosphorylase b to methotrexate, whereas glycogen does not influence the methotrexate binding to the enzyme. Methotrexate, folic and folinic acids are found to be inhibitors of the muscle glycogen phosphorylase b. The inhibition is reversible and characterized by positive kinetic cooperativity (the Hill coefficient exceeds one unity). The value of the pterin concentration causing two-fold diminishing of the enzymatic reaction rate increased in the order: folic acid (0.65 mM), methotrexate (1.01 mM), folinic acid (3.7 mM). The antagonism between methotrexate, folic and folinic acids, on the one hand, and AMP and FMN, on the other, is revealed for their combined action.

Adenosine Monophosphate↗
PubMedDate not supplied

[Effect of a centrogenic fever on phosphorylase and pyruvate kinase activity in rabbit tissues].

Administration of pyrogenal into rabbits caused a decrease in the activity of phosphorylase A and pyruvate kinase in musculus gastrocnemius as well as pyruvate kinase -- in musculus soleus. The phosphorylase A activity was increased within 3 hrs after the drug administration but it was decreased after the treatment for three days. Administration of hydrocortisone decreased the activity of phosphorylase and pyruvate kinase in both muscles. Activities of total phosphorylase and phosphorylase A were decreased simultaneously with restoration of the pyruvate kinase activity in the both muscles after the complex administration of pyrogenal and hydrocortisone within 3 days. In liver tissue and kidney cortex activities of the enzymes did not differ from those of control animals under all the conditions studied. The various extent and direction in alterations of the same enzymes in dissimilar tissues of a single amnial after administration of pyrogenal and hydrocortisone were considered as the various adaptation of cells of different tissues to the effect of hydrocortisone and as the alteration in tissue reactivity in experimental fever animals to the hormonal effect.

Animals↗
PubMed1977

Role of tetramer in equilibrium dimer equilibrium in the dephosphorylation and activity of phosphorylase a.

Skeletal muscle phosphorylase a exists as a tetramer or a dimer depending upon the temperature and protein concentration. The rate of dephosphorylation by phosphorylase phosphatase is very low at 18 degrees C where phosphorylase a exists as a tetramer. Caffeine markedly increases the rate of dephosphorylation of tetrameric phosphorylase a at 18 degrees C but has no effect on the dephosphorylation of the dimeric form. Caffeine also enhances the enzymic activity of phosphorylase a at 18 degrees C. The results presented here indicate that caffeine can shift the tetramer in equilibrium dimer equilibrium toward the dimeric form at 18 degrees C. This conclusion in supported by sedimentation analyses.

Caffeine↗