Phosphorylase

Substrate properties of xanthine (Xan) and xanthosine (Xao) for purine nucleoside phosphorylases (PNP) of mammalian origin have been reported previously, but only at a single arbitrarily selected pH and with no kinetic con-stants. Additionally, studies have not taken into account the fact that, at physiological pH, Xao (pKa¼5.7) is a mono-anion, while Xan (pKa¼7.7) is an equilibrium mixture of the neutral and monoanionic forms.

10p research12 23-04-2013 40 2   Download

Multiple signalling pathways are involved in themechanism by which insulin stimulates hepatic glycogen synthesis. In this study we used selective inhibitors of glycogen synthase kinase-3 (GSK-3) and an allosteric inhibitor of phosphory-lase (CP-91149) that causes dephosphorylation of phos-phorylasea, to determine the relative contributions of inactivation of GSK-3 and dephosphorylation of phos-phorylaseaas alternative pathways in the stimulation of glycogen synthesis by insulin in hepatocytes.

9p fptmusic 16-04-2013 40 3   Download

Glycogen phosphorylases (GPs) constitute a family of widely spread catabolica1,4-glucosyltransferases that are active as dimers of two identical, pyridoxal 5¢-phosphate-containing subunits. In GP fromCorynebacterium callunae, physiological concentrations of phosphate are required to inhibit dissociation of protomers and cause a 100-fold increase in kinetic stability of the functional quarternary structure.

11p fptmusic 16-04-2013 34 2   Download

We report herein the first molecular characterization of 5¢-deoxy-5¢-methyl-thio-adenosine phosphorylase II from Sulfolobus solfataricus(SsMTAPII). The isolated gene of SsMTAPII was overexpressed inEscherichia coli BL21. Purified recombinant SsMTAPII is a homohexamer of 180 kDa with an extremely low Km(0.7lm) for 5¢-deoxy-5¢-methylthioadenosine. The enzyme is highly thermophilic with an optimum temperature of 120
C and extremely thermostable with an apparent Tmof 112
C that increases in the presence of substrates....

14p awards 06-04-2013 33 4   Download

Phosphorylase kinase (PhK) is a large hexadecameric enzyme consisting of four copies of four subunits: (abcd)4. An intrinsic calmodulin (CaM, the d subunit) binds directly to the cprotein kinase chain. The interaction site of CaM onchas been localized to a C-terminal extension of the kinase domain. Two 25-mer peptides derived from this region, PhK5 and PhK13, were identified previously as potential CaM-binding sites.

12p awards 06-04-2013 37 4   Download

The extremely heat-stable 5¢-methylthioadenosine phos-phorylase from the hyperthermophilic archaeonPyrococcus furiosuswas cloned, expressed to high levels inEscherichia coli, and purified to homogeneity by heat precipitation and affinity chromatography. The recombinant enzyme was subjected to a kinetic analysis including initial velocity and product inhibition studies. The reaction follows an ordered Bi–Bi mechanism and phosphate binding precedes nucleo-side binding in the phosphorolytic direction....

11p awards 05-04-2013 39 2   Download

Using 0.4Mimidazole citrate buffer (pH 7.5) containing 0.1 mML-cysteine, homodimeric starch phosphorylase from Corynebacterium calluane(CcStP) was dissociated into native-like folded subunits concomitant with release of pyridoxal 5¢-phosphate and loss of activity. The inactivation rate of CcStP under resolution conditions at 30
Cwas, respectively, four- and threefold reduced in two mutants, Arg234fiAla and Arg242fiAla, previously shown to cause thermostabilization of CcStP [Griessler, R., Schwarz, A., Mucha, J.&Nidetzky, B. ...

11p awards 05-04-2013 41 5   Download

HPr kinase/phosphorylase (HPrK/P) is the key regulator of carbon metabolism in many Gram-positive bacteria. It phosphorylates/dephosphorylates the HPr protein of the bacterial phosphotransferase system on a regulatory serine residue in response to the nutrient status of the cell. In Mycoplasma pneumoniae,HPrK/P is one of the very few regulatory proteins encoded in the genome.

8p dell39 03-04-2013 44 2   Download

Hepatic insulin resistance in the leptin-receptor defective Zucker fa⁄fa rat is associated with impaired glycogen synthesis and increased activity of phosphorylase-a. We investigated the coupling between phosphorylase-a and glycogen synthesis in hepatocytes from fa⁄fa rats by modulating the concentration of phosphorylase-a.

11p inspiron33 26-03-2013 42 4   Download

We report here the characterization of the first mammalian-like purine nucleoside phosphorylase from the hyperthermophilic archaeonPyrococcus furiosus (PfPNP). The gene PF0853 encoding PfPNP was cloned and expressed in Escherichia coliand the recombinant protein was purified to homogeneity.

14p galaxyss3 21-03-2013 44 4   Download

At the optimal temperature (65C),Thermus thermophiluspolynucleotide phosphorylase (Tth PNPase), produced inEscherichia colicells and isolated to functional homogeneity, completely destroys RNAs that possess even a very stable intramolecular secondary structure, but leaves intact RNAs whose 3¢ end is protected by chemical modification or by hybridization with a complementary oligonucleotide.

13p media19 06-03-2013 43 3   Download

Schizophyllum commune a,a-trehalose phosphorylase utilizes a glycosyl-transferase-like catalytic mechanism to convert its disaccharide substrate into a-d-glucose 1-phosphate and a-d-glucose. Recruitment of phosphate by the free enzyme inducesa,a-trehalose binding recognition and promotes the catalytic steps.

11p media19 05-03-2013 26 2   Download

101. Cấu trúc của hormone là những: A. Protein B. Dẫn xuất của acid amine C. Steroid D. A,B,C đều đúng E. A,B,C đều sai. 102. Hormone chỉ có tác dụng khi được gắn với: A. AMP vòng B. Receptor C. ADN D. Adenyl cyclase E. Proteinkinase 103.Adrenalin sau khi gắn vào receptor có tác dụng hoạt hoá trực tiếp: A. ATP B. Adenyl cyclase C. Proteinkinase D. Phosphorylase E. Glycogen synthetase

10p m310dy1ndark 05-03-2013 116 15   Download

His334 facilitates catalysis byCorynebacterium callunaestarch phosphory-lase through selective stabilization of the transition state of the reaction, partly derived from a hydrogen bond between its side chain and the C-6 hydroxy group of the glucosyl residue undergoing transfer to and from phosphate.

11p media19 04-03-2013 38 2   Download

A gene cluster involved in maltodextrin transport and metabolism was identified in the genome of Lactobacillus acidophilus NCFM, which encoded a maltodextrin-binding protein, three maltodextrin ATP-binding cassette transporters and five glycosidases, all under the control of a tran-scriptional regulator of the LacI-GalR family.

13p vinaphone15 28-02-2013 57 4   Download

5¢-Deoxy-5¢-methylthioadenosine phosphorylase II fromSulfolobus solfatari-cus (SsMTAPII) and purine nucleoside phosphorylase from Pyrococcus furiosus (PfPNP) are hyperthermophilic purine nucleoside phosphorylases stabilized by intrasubunit disulfide bonds. In their C-terminus, both enzymes harbour a CXC motif analogous to the CXXC motif present at the active site of eukaryotic protein disulfide isomerase.

7p viettel02 20-02-2013 36 3   Download

Genetic deficiency of purine nucleoside phosphorylase (PNP; EC 2.4.2.1) activity leads to a severe selective disorder of T-cell function. Therefore, potent inhibitors of mammalian PNP are expected to act as selective immunosuppressive agents against, for example, T-cell cancers and some autoimmune diseases.

14p mobifone23 18-01-2013 52 5   Download

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Pig gene mapping : assignment of the genes for mannosephosphate isomerase (MPI) and nucleoside phosphorylase (NP) to chromosome no

10p toshiba21 16-11-2011 45 3   Download

Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học quốc tế cung cấp cho các bạn kiến thức về ngành y đề tài: Quantification of the glycogen cascade system: the ultrasensitive responses of liver glycogen synthase and muscle phosphorylase are due to distinctive regulatory designs

18p toshiba17 31-10-2011 57 4   Download

CHUYỂN HOÁ GLYCOGEN * Thoái biến glycogen: - Xảy ra chủ yếu ở gan và ở cơ. - SP tạo: glucose hoặc G-1P G- Gồm 3 giai đoạn: 1- Phân cắt glycogen: - Tạo G-1P: G3 E (phosphorylase “a”, E chuyển, và E cắt nhánh.

5p artemis04 07-09-2011 323 62   Download