Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Ca2+ -dependent phosphorylation of proteins has been recognized as a major regulatory mechanism of biological processes. In the heart, protein kinases that are activated by Ca2+ include phosphorylase kinase, myosin light chain kinase, phospholamban kinase [review in 4], and the kinases responsible for phosphorylation of endogenous proteins in the membrane [11] and soluble [6] fractions of the cell. All of these Ca2+-dependent enzymes require the presence, either as an enzyme subunit or as a cofactor, of calmodulin, a Ca2+-binding protein which is involved in various other Ca2+-requiring reactions or processes [review in 3]. We demonstrate here the presence, in the rat heart, of a soluble calmodulin-dependent protein kinase which seems different from those already described in this tissue. The substrate for this enzyme is a 43 kdaltons protein, present in the same soluble fraction.
J Mol Cell Cardiol 1983 Jan
PMID:Phosphorylation of a 43 kdaltons protein from rat heart by a calmodulin-dependent protein kinase. 684 15

The presence of two interconvertible forms of phosphorylase kinase has been confirmed in rat liver extracts. The pH optimum of the nonactivated form (PhK b) was lower than the pH optimum of the activated form (PhK a) as reported by others (2). In the absence of calcium the Km of PhK b for phosphorylase b was 53 +/- 10 U/ml with a Vm of 17 +/- 1 U/gm of tissue. The Km of PhK a for phosphorylase b was 20 +/- 2 U/ml with a Vm of 65 U/gm. Calcium stimulated both forms of phosphorylase kinase (A0.5 approximately 0.03 micro). In the presence of 0.1 microM calcium the Km for phosphorylase b of both forms of the enzyme was reduced. In addition, calcium increased the Vm of both forms, but the effect was greater for PhK b than for PhK a. The Km of both forms of phosphorylase kinase for ATP was 0.05 mM and was unaffected by calcium. All of these studies were done using liver phosphorylase b as substrate. Conditions for assaying PhK a activity virtually independent of PhK b activity also are indicated. This will enable the monitoring of interconversion reactions in tissue extracts. Phosphorylase kinase a was purified to near homogeneity using DEAE-cellulose, Sepharose 4B gel filtration and ATP affinity chromatography. The molecular weight was approximately 1 x 10(6). The pH profile, calcium requirements and kinetic constants were the same as those for PhK a in the crude extract.
Mol Cell Biochem 1982 Aug 20
PMID:Liver phosphorylase kinase: characterization of two interconvertible forms and partial purification of phosphorylase kinase a. 713 65

An epitope of the alpha-subunit of phosphorylase kinase from fast-twitch skeletal muscle was localized to the tips of the bilobal kinase molecule by two types of immunoelectron microscopy. This is the first direct evidence identifying the location of any of the enzyme's 16 subunits within the phosphorylase kinase molecule. Negatively stained complexes of phosphorylase kinase with an immunoglobulin G monoclonal antibody specific for the alpha-subunit (mAb 157) were observed by conventional transmission electron microscopy, and complexes of the unstained enzyme with undecagold-labeled Fab' fragments derived from mAb 157 were visualized by scanning transmission electron microscopy. Images from both techniques indicate a symmetrical arrangement of the epitope, consistent with a "head-to-head" packing arrangement of the four alpha-subunits. In Western blots, mAb 157 crossreacted with comigrating fragments obtained by digesting non-denatured phosphorylase kinase with a variety of proteases, suggesting that the epitope for the anti-alpha mAb is contained within a protease-resistant domain. Partial sequencing of a 24.1 kDa immunoreactive chymotryptic fragment narrowed the epitope to somewhere within the carboxyl-terminal one-sixth of the alpha-subunit. Studies of the crossreactivity of mAb 157 with the holoenzyme in the presence of calmodulin, after phosphorylation or with different isoforms (all with known alpha-subunit sequence targets or differences), suggest that the epitope is even more proximal to the carboxyl terminus. This epitope was not implicated in any known function or activity of the enzyme, suggesting that the region proximal to the carboxyl terminus of the alpha-subunit, and thus to the lobe tips of the hexadecamer, may have a role other than catalytic or regulatory.
J Mol Biol 1994 Jan 21
PMID:An epitope proximal to the carboxyl terminus of the alpha-subunit is located near the lobe tips of the phosphorylase kinase hexadecamer. 750 77

X-linked liver glycogenosis (XLG) due to liver phosphorylase kinase (PHK) deficiency is the most frequent liver glycogen storage disease. The affected patients present in early childhood with hepatomegaly and growth retardation. We isolated and determined the structure of human liver alpha subunit of PHK (PHKA2) cDNA. The 3705 base pair open reading frame encodes a polypeptide of 1235 amino acid residues, and the deduced amino acid sequence shows 93 and 68% homology to that of rabbit liver alpha subunit of PHK and human muscle alpha subunit of PHK, respectively. We identified a missense mutation, a valine substitution for glycine at amino acid 193, in the PHKA2 gene of a family with XLG.
Biochem Mol Biol Int 1995 Jul
PMID:Isolation of cDNA encoding the human liver phosphorylase kinase alpha subunit (PHKA2) and identification of a missense mutation of the PHKA2 gene in a family with liver phosphorylase kinase deficiency. 754 48

The focus of this study was to identify the molecular basis for the hypersensitive response of glycogen phosphorylase activation to epinephrine stimulation in alloxan diabetic-derived cardiomyocytes. Cyclic AMP levels were found not to be significantly different between normal and diabetic-derived cells while cGMP concentrations were found consistently to be significantly lower in diabetic-derived cells than in normal cells. Treatment with cyclic GMP analogues did not affect phosphorylase activation by epinephrine in normal cardiomyocytes whereas, IBMX, a nonselective phosphodiesterase inhibitor, had a significant effect on basal and agonist-stimulated phosphorylase activity in both normal and diabetic-derived cardiomyocytes. Differences in the time course for the rate of decay of phosphorylase a from agonist-stimulated to basal levels were observed between normal and diabetic cells. After 3 h in primary culture, phosphorylase a activity returned to basal levels more quickly in normal than in diabetic-derived cells while after 24 h in culture, the time for phosphorylase a decay was not significantly different between normal and diabetic myocytes and was longer than the 3 h response. After 3 h response. After 3 h in primary culture, no significant difference in phosphorylase kinase activity was observed between normal and diabetic-derived cells exposed to epinephrine whereas, after 24 h in culture, phosphorylase kinase activity was significantly decreased in diabetic cells under basal and agonist-stimulation conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1995 Apr 26
PMID:Identification of the molecular basis for phosphorylase hypersensitivity in cultured diabetic cardiomyocytes. 767 33

Pentosan polysulfate, a polyanionic mucopolysaccharide, which has been shown to exert inhibitory effects on human immunodeficiency virus (HIV-I) replication, inhibited the activities of protein tyrosine kinases from lymphocytes (Jurkat cells) and rat lung in a concentration dependent manner. In addition, the autophosphorylation of p56lck, a lymphocyte associated protein tyrosine kinase from Jurkat cells was also inhibited by pentosan polysulfate (100 micrograms/ml). Furthermore, the activities of protein serine/threonine kinases such as Ca2+, phospholipid-dependent protein kinase (protein kinase C) from human platelets and the catalytic subunit of cAMP-dependent protein kinase from skeletal muscle were also inhibited by this mucopolysaccharide. However, the activity of phosphorylase kinase was not altered. The inhibition of rat lung protein tyrosine kinase was rapid and competitive with respect to ATP with an apparent Ki value of 5-20 micrograms/ml. These results suggest that the ability of pentosan polysulfate to inhibit various protein serine/threonine and tyrosine kinases may be one of the mechanisms by which this compound exerts its inhibitory effect of HIV-I replication.
Mol Cell Biochem 1993 Mar 24
PMID:Pentosan polysulfate, a potent anti HIV and anti tumor agent, inhibits protein serine/threonine and tyrosine kinases. 768 45

Using site-directed mutagenesis, we proposed that an autoinhibitory domain(s) is located at the C-terminal region (301-386) of the phosphorylase kinase gamma-subunit (Huang, C.-Y.F., Yuan C.-J., Livanova, N.B., and Graves, D.J. (1993) Mol. Cell. Biochem. 127/128, 7-18). Removal of the putative inhibitory domain(s) by truncation results in the generation of a constitutively active and calmodulin-independent form, gamma 1-300. To probe the structural basis of autoinhibition of gamma-subunit activity, two synthetic peptides, PhK13 (gamma 303-327) and PhK5 (gamma 343-367), corresponding to the two calmodulin-binding regions, were assayed for their ability to inhibit gamma 1-300. Competitive inhibition of gamma 1-300 by PhK13 was found versus phosphorylase b (Ki = 1.8 microM) and noncompetitive inhibition versus ATP. PhK5 showed noncompetitive inhibition with respect to both phosphorylase b and ATP. Calmodulin released the inhibition caused by both peptides. These results indicate that there are two distinct auto-inhibitory domains within the C terminus of the gamma-subunit and that these two domains overlap with the calmodulin-binding regions. Two mutant forms of gamma 1-300, E111K and E154R, were used to probe the enzyme-substrate-binding region using peptide substrate analogs corresponding to residues 9-18 of phosphorylase b (KRK11Q12ISVRGL). The data suggest that Glu111 interacts with the P-3 position of the substrate (Lys11) and Glu154 interacts with the P-2 site (Gln12). Both E111K and E154R were competitively inhibited with respect to phosphorylase b by PhK13, with 14- and 8-fold higher Ki values, respectively, than that observed with the wild-type enzyme. These data are consistent with a model for the regulation of the gamma-subunit of phosphorylase kinase in which PhK13 acts as a competitive pseudosubstrate that directly binds the substrate binding site of the gamma-subunit (Glu111 and Glu154).
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PMID:Identification of the substrate and pseudosubstrate binding sites of phosphorylase kinase gamma-subunit. 770 57

Glycogen phosphorylase b has been purified to homogeneity from the fat body of larval Manduca sexta. The purification procedure involved ammonium sulfate precipitation, and chromatography of DEAE-cellulose, 5'-AMP-Sepharose and Q-Sepharose. The final product, which showed a single band on SDS-PAGE with a M(r) = 92,500, was purified 50-fold from the original homogenate in a yield of about 3%. The molecular mass of the native purified phosphorylase b was estimated to be 186,000 Da from gel filtration, suggesting that the native enzyme is a dimer. The apparent Km values for glycogen, phosphate and 5'-AMP were 1.4 mM, 82 mM and 1.1 mM, respectively. The enzyme had a pH optimum of 7.05, and was inhibited by ATP, ADP and glucose, but not by trehalose, even at high concentration. Conversion of phosphorylase b into the a form was achieved by incubation with rabbit phosphorylase kinase and Mg(2+)-ATP. The molecular mass of phosphorylase a was estimated to be 250,000 Da by gel filtration chromatography. The specific activity of the a form in the presence of 5'-AMP was 1.6-1.7-fold higher than the specific activity of the b form under the same conditions. Thus, 5'-AMP activates the a form by about 20%, whereas ATP has no effect on the phosphorylase a activity.
Insect Biochem Mol Biol 1995 Feb
PMID:Purification and properties of glycogen phosphorylase from the fat body of larval Manduca sexta. 771 51

The enzyme termed nowadays protein kinase CK2 was first described in liver extracts (as a mixture with protein kinase CK1), using casein as artificial substrate, by Burnett and Kennedy (1954). In 1960 it was shown that such casein/phosvitin phosphorylating activity was ubiquitous and distinct from phosphorylase kinase, i.e., the only other protein kinase known at that time. CK1 and CK2 were distinguished from each other at the end of the sixties, and during the seventies CK2 was purified to homogeneity in several laboratories and thoroughly characterized as far as its subunit structure (alpha 2 beta 2), site specificity, and in vitro responsiveness to various effectors were concerned. The first endogenous substrate for CK2 (eIF-3) was described in 1976, but it was during the eighties that it became clear that CK2 is a pleiotropic protein kinase committed with the phosphorylation of a myriad of cellular targets. More than 100 CK2 substrates are known, sharing typical phosphoacceptor sites specified by multiple acidic residues on the C terminal side of Ser/Thr. The definition of the primary structure of CK2 catalytic subunit, in 1987, definitely included CK2 in the big family of eukariotic protein kinases. The growing interest for CK2 is accounted for by its unusual properties, by the increasing number of its substrates, and by several coincidental arguments suggesting that this pleiotropic protein kinase plays a fundamental role in cellular regulation. A major and intriguing problem concerning CK2 is its apparent lack of regulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Cell Mol Biol Res 1994
PMID:A historical view of protein kinase CK2. 773 12

Heritable phosphorylase kinase (Phk) deficiency is responsible for several forms of glycogen storage disease in humans and animals that differ in mode of inheritance and tissue-specificity. Mutations affecting different subunits and isoforms of Phk are expected to contribute to this heterogeneity. In the present study, we have investigated a case of muscle-specific, adult-onset Phk deficiency. The coding sequences of three candidate genes were analyzed by RT-PCR and sequencing: the muscle isoform of the alpha subunit (alpha M), a muscle-specifically expressed exon of the beta subunit, and the muscle isoform of the gamma subunit. Whereas the latter two sequences were found to be normal, we identified a nonsense mutation in alpha M. The condition of this patient therefore is a human homolog of the X-linked muscle Phk deficiency of I-strain mice. To our knowledge, this is the first description of a human Phk deficiency mutation.
Hum Mol Genet 1994 Nov
PMID:Human muscle glycogenosis due to phosphorylase kinase deficiency associated with a nonsense mutation in the muscle isoform of the alpha subunit. 787 15


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