Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies on the gonadotrophin-responsive adenylyl cyclase (AC) system of rabbit and porcine ovarian follicles reveal that hCG or LH-induced desensitization of the AC system can be divided into two phases: an initial, LH-specific phase and a second phase which is not specific for LH. The first phase occurs within the first hour after LH-hCG-receptor interaction, is agonist specific, and is not mediated by protein synthetic events or by cAMP. In view of our previous demonstration of the critical dependence of the LH-induced desensitizing process in cell-free membrane preparations of porcine follicles upon Mg2+ and ATP, we investigated the role of a phosphorylation reaction in the first phase of the AC desensitizing process. Porcine follicular membranes rich in LH-sensitive AC activity were found to contain the molecular requirements necessary for a phosphorylation reaction: namely, cAMP-dependent and cAMP-independent protein kinases as well as phosphoprotein phosphatases. The following lines of indirect evidence indicated that reversal or resensitization of the desenzitized AC system to LH was mediated by a dephosphorylation reaction. Activators of endogenous phosphoprotein phosphatases--Mn2+ and dithiothreitol--promoted a specific resensitization of the follicular AC system to LH. Likewise, a partially purified phosphoprotein phosphatase also resensitized the desensitized, LH unresponsive AC to LH, and boiling of the phosphatase prevented its effect. LH-induced desensitization of the AC system, on the other hand, did not appear to be mediated by a cAMP-dependent protein kinase, as evidenced both by the inability of beef heart protein to promote desensitization of AC and by the inability of an inhibitor of cAMP-dependent protein kinase to prevent LH-induced densensitization. The second phase of desensitization, which occurs after the first hour following hCG-LH-receptor interaction, is characterized by a loss of responsiveness to FSH as well as to LH and can be promoted by dibutryl cAMP (in the absence of LH). These results provide new evidence on the characteristics and molecular mechanism of LH-induced densensitization of the follicular AC system. These results indicate that the level of phosphorylation of membrane-associated components may, in part, regulate the activity of the AC system during this first phase of homologous desensitization.
...
PMID:LH-induced desensitization of the adenylyl cyclase system in ovarian follicles. 22 90

Synaptosomal plasma membranes from mammalian brain contain protein kinase activity which phosphorylates endogenous membrane proteins and is stimulated by cyclic AMP. Using polyacrylamide gel electrophoresis it was shown that at least ten proteins in the synaptosomal plasma membrane fraction could be phosphorylated by endogenous cyclic AMP-stimulated protein kinase activity. The number of proteins whose phosphorylation was stimulated by cyclic AMP was strongly influenced by the pH and Mg2+ concentration used in the phosphorylation reaction. A complex pattern of cyclic AMP-stimulated protein phosphorylation was obtained only with synaptosomal plasma membranes and a crude microsomal fraction. Mitochondrial and myelin fractions exhibited no cyclic AMP-stimulated protein kinase activity. Investigation of the distribution of substrates for cyclic AMP-stimulated phosphorylation among various brain regions failed to reveal any regional differences.
...
PMID:Synaptic membrane proteins as substrates for cyclic AMP-stimulated protein phosphorylation in various regions of rat brain. 22 25

The phosphorylation of two purified vaccinia virus proteins (Acceptors I and II) by a protein kinase isolated from vaccinia virus cores has been studied. Phosphorylation of viral acceptor proteins by the purified enzyme was dependent on the presence of ATP, Mg2+, and protamine or other basic proteins, and was maximal at alkaline pH values. Cyclic mononucleotides did not stimulate the vaccinia protein kinase under a variety of conditions. Protamine, however, was shown to function as an enzyme activator. In its presence, the purified vaccinia protein kinase phosphorylated mainly serine residues in Acceptor I, and predominantly threonine residues in Acceptor II. Phosphorylation of protamine accounted for less than 1% of the total 23P incorporation. Tryptic peptide maps prepared from 32P-labeled Acceptors I and II demonstrated that they contained different labeled peptide sequences and were, therefore, distinct protein species. From additional studies on both purified and virus-associated protein kinase it was concluded that various proteins affected the protein kinase reaction in one of three ways. One class of proteins served as phosphate acceptors, but only when another activator protein was present. A second class consisted of proteins that were strong activators but poor phosphate acceptors. The third class contained proteins that were fair phosphate acceptors, but which also activated the phosphorylation of other acceptor proteins.
...
PMID:Characterization of a protein kinase and two phosphate acceptor proteins from vaccinia virions. 23 13

Adenosine 3',5'-monophosphate (cAMP) dependent protein kinase (EC 2.7.1.37) catalyzes the phosphorylation of serine and threonine residues of a number of proteins according to the following chemical equation: ATP + protein leads to phosphoprotein + ADP. The DEAE-cellulose peak II holoenzyme from bovine brain, which is composed of regulatory and catalytic subunits, is resistant to ethoxyformic anhydride inactivation. After adding cAMP, the protein kinase becomes susceptible to ethoxyformic anhydride inhibition. Ethoxyformic anhydride (2mM) inhibits the enzyme 50% (5 min, pH 6.5, 30 degrees) in the presence of 10 muM cAMP, but less than 5% in its absence. The substrate, Mg2+-ATP, protects against inactivation suggesting that inhibition is associated with modification of the active site. Addition of regulatory subunit or Mg2+-ATP to the isolated catalytic subunit also prevents ethoxyformic anhydride inactivation. These results suggest that the regulatory subunit shields the active site of the catalytic subunit thereby inhibiting it. In contrast to the bovine brain or muscle DEAE-cellulose peak II holoenzyme, the bovine muscle peak I holoenzyme is susceptible to ethoxyformic anhydride inactivation in the absence of cAMP.
...
PMID:Bovine brain adenosine 3',5'-monophosphate dependent protein kinase. Mechanism of regulatory subunit inhibition of the catalytic subunit. 24 Apr 4

Purified cyclic adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase of bovine cardiac muscles catalyzes the incorporation of 2 mol of 32P from [gamma-32P]ATP to seryl residues in its cAMP-binding protein. The reaction appears to be catalyzed by the protein kinase itself rather than by a protein kinase kinase and is enhanced by cAMP and by the addition of polyarginine. Phosphorylation of the purified enzyme facilitates its dissociation by cAMP (Erlichman, J., Rosenfeld, R., and Rosen, O.M. (1974) J. Biol. Chem. 249, 5000-5003) but does not affect cAMP binding. At equilibrium, 2 mol of cAMP are bound to both the phospho- and dephospho-enzymes. Phosphorylation of protein kinase is reversible. Upon addition of ADP and Mg2+, phosphate is transferred from the protein to ADP, and ATP is formed. The reverse reaction is optimal at pH 5.5 unlike the forward reaction which has a broad, more alkaline pH activity optimum. It is activated by polyarginine and dependent upon the addition of cAMP to a much greater degree than the forward reaction. The data suggest that the catalytic subunit of protein kinase catalyzes the forward and reverse reactions but do not exclude the possibility that the holoenzyme may also be active. Autophosphorylation by protein kinase and dephosphorylation by phosphrprotein phosphatases of by reverals of the autophosphorylation reaction may regulate the sensitivity of certain protein kinases to activation by cAMP in vivo.
...
PMID:Reversible autophosphorylation of a cyclic 3':5'-AMP-dependent protein kinase from bovine cardiac muscle. 24 Aug 40

A physiologically and biochemically realistic model of the regulation of pyruvate dehydrogenase complex (PDH) was constructed for the perfused rat heart. It includes conversion between inactive (phospho) and active (dephospho) forms by a specific protein kinase (PDHK) and phosphoprotein phosphatase (PDHP). The activity of the tightly bound PDHK is influenced by synergistic activation/inhibition by acetyl CoA/CoASH and NADH/NAD. PDHK in this simulation was more sensitive to the fraction of ADP that was Mg2+-chelated than to the ATP-to-ADP ratio. Ca2+ stimulates binding of Mg2+-dependent PDHP to the complex; the bound enzyme was considered to be the active species. The fraction of PDH in the active form, rather than substrate and inhibitor levels, determines PDH activity under these conditions. This fraction depends on the present value and recent history of the difference between PDHK and PDHP activities. Both of these are active continuously and continuously control PDH.
...
PMID:Computer simulation of metabolism in pyruvate-perfused rat heart. III. Pyruvate dehydrogenase. 47 88

Myosin light chain kinase, which is located primarily in the soluble fraction of bovine myocardium, has been isolated and purified approximately 1200-fold with 16% yield by a three-step procedure. The approximate content of soluble myosin light chain kinase in heart is calculated to be 0.63 microM. The isolated kinase is active only as a ternary complex consisting of the kinase, calmodulin, and Ca2+; the apparent Kd for calmodulin is 1.3 nM. The enzyme also exhibits a requirement for Mg2+ ions. Myosin light chain kinase is a monomeric enzyme with Mr = 85,000. The enzyme exhibits a Km for ATP of 175 microM, and a K0.5 for the regulatory light chain of cardiac myosin of 21 microM. The optimum pH is 8.1. Kinase activity is specific for the regulatory light chain of myosin. The specific activity of the isolated enzyme (30 nmol 32P/min/mg of protein) is considerably less than and corresponding values reported for the skeletal and smooth muscle light chain kinases. This is probably due to proteolysis during extraction of the myocardium, a phenomenon which has, as yet, proven impossible to eliminate. In contrast to the smooth muscle enzyme (Adelstein, R.S., Conti, M.A., Hathaway, D.R., and Klee, C.B. (1978) J. Biol. Chem. 253, 8347-8350), the cardiac kinase is not phosphorylated by the catalytic subunit of cAMP-dependent protein kinase.
...
PMID:Purification and characterization of bovine cardiac calmodulin-dependent myosin light chain kinase. 50 Jul 1

Myelin isolated from the rat peripheral nervous system (sciatic nerve and cauda equina) contained Mg2+-dependent protein kinase that phosphorylated myelin polypeptides. Ca2+, in micromolar concentrations, markedly stimulated phosphorylation (half-maximal stimulation at 5 microM (free) Ca2+) but at higher concentrations (greater than 100 microM Ca2+) it caused inhibition. In the presence of Triton X-100, phosphorylation (+/-Ca2+) of myelin was increased and Ca2+ caused up to a 10-fold increase in phosphorylation. Among the myelin polypeptides, P0 (Mr, 28 000), a major glycoprotein, accounted for nearly 60% of the total phosphate incorporated into the myelin and Ca2+ markedly promoted phosphorylation of P0. Phosphorylation of other myelin polypeptides, P2 (Mr, 16 000), Y (Mr, 26 000), and P1 (Mr, 20 000), and the Ca2+-stimulatory effect on phosphorylation of these were also evident. Cyclic AMP (or other cyclic nucleotides) failed to show any significant stimulatory effect on myelin phosphorylation.
...
PMID:Calcium ion stimulated endogenous protein kinase catalyzed phosphorylation of peripheral nerve myelin proteins. 50 75

The protein synthesis initiation factor eIF-3 (a multicomponent protein complex) was labelled with 32P by phosphorylation with a protein kinase present in a partially purified 'hemin-controlled repressor' preparation. The interaction of the labelled factor with the 40 S ribosomal subunit during the course of initiation was followed. It binds to the 40 S subunit in the absence of other initiation factors and inhibits the Mg2+-dependent reassociation of the 40 S with the 60 S ribosomal subunit. It stimulates the binding of the ternary complex (eIF-2, GTP, Met-tRNAf) to the 40 S subunit, and earlier work (Trachsel, H., Schreier, M.H., Erni, B. and Staehelin, T. (1977) J. Mol. Biol. 116, 745-767) also showed it to be essential for the subsequent binding of mRNA. The factor is released from the 40 S initiation complex during the 60 S subunit joining reaction.
...
PMID:Initiation of mammalian protein synthesis. The multiple functions of the initiation factor eIF-3. 51 82

A tri-, di-, and monoacylglycerol-hydrolyzing enzyme from rat adipose tissue has been detergent-solubilized and separated from monoacylglycerol lipase (H. Tornqvist and P. Belfrage, 1976, J. Biol. Chem. 251, 813-819) and lipoprotein lipase by use of ion-exchange chromatography, broad and narrow pH range electrofocusing and gel chromatography. The final preparation contained several different proteins. One of these, with an apparent minimum molecular weight of 86,000 by SDS-gel electrophoresis, was identified as the enzyme protein of hormone-sensitive lipase: a) the enzyme activity was reproducibly stimulated 50-100% by incubation with cyclic AMP-dependent protein kinase, cyclic AMP and ATP-Mg2+; b) the relative intensity of the Mw 86,000 protein band, and only this, closely paralleled the enzyme activity during narrow pH range electrofocusing and during subsequent gel chromatography of the electrofocusing enzyme peak fraction; c) only the Mw 86,000 protein extensively incorporated 32p from [gamma-32P]ATP after incubation with protein kinase and cyclic AMP. The pI of the enzyme was 6.7, it had the same Stokes radius on Sephadex G 200 as IgG and was 50% inactivated by 10 micron HgCl2, 20 micron PCMB, 50 micron DFP, 10 mM NaF and non-ionic detergents above their critical micellar concentration.
...
PMID:Identification and some characteristics of the enzyme protein of the hormone-sensitive lipase from rat adipose tissue. 66 58


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---