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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Upon fractionation of a post mitochondrial supernatant from rat liver, phosphorylase kinase activity was largely recovered in the cytosol and the smooth endoplasmic reticulum (SER) fraction. The presence of phosphorylase kinase in SER vesicles was not due to an interaction of the enzyme with glycogen particles, since previous elimination of SER glycogen either by 48 h animal starvation or by treatment of the membrane fraction with alpha-amylase did not significantly alter phosphorylase kinase activity content. Washing of the initial pellet of SER fraction (crude SER) by dilution and recentrifugation, released in the supernatant an amount of phosphorylase kinase activity, which is dependent on: i) the degree of dilution, ii) the number of washes, iii) the ionic strength of the washing solution and iii) the presence or absence of Ca2+. Crude SER-associated phosphorylase kinase was marginally affected by increased concentrations of antibody against rabbit skeletal muscle holoenzyme which nevertheless drastically inhibited cytosolic enzyme activity, while it showed a higher resistance to partial proteolysis and a different Western blotting profile with anti-phosphorylase kinase when compared with the soluble kinase. A small but significant fraction of SER phosphorylase kinase was strongly associated with the microsomal fraction being partly extractable only in presence of detergents. This membrane-bound enzyme form exhibited an alkaline pH optimum, in contrast to the neutral pH optima of both soluble and weakly associated phosphorylase kinase.
Mol Cell Biochem 1996 Jan 26
PMID:The association of phosphorylase kinase with membranes of rat liver smooth endoplasmic reticulum. 871 29

X-linked liver glycogenosis type II (XLG II) is a recently described X-linked liver glycogen storage disease, mainly characterized by enlarged liver and growth retardation. These clinical symptoms are very similar to those of XLG I. In contrast to XLG I patients, however, XLG II patients do not show an in vitro enzymatic deficiency of phosphorylase kinase (PHK). Recently, mutations were identified in the gene encoding the liver alpha subunit of PHK (PHKA2) in XLG I patients. We have now studied the PHKA2 gene of four unrelated XLG II patients and identified four different mutations in the open reading frame, including a deletion of three nucleotides, an insertion of six nucleotides and two missense mutations. These results indicate that XLG II is due to mutations in PHKA2. In contrast to XLG I, XLG II is caused by mutations that lead to minor structural abnormalities in the primary structure of the liver alpha subunit of PHK. These mutations are found in a conserved RXX(X)T motif, resembling known phosphorylation sites that might be involved in the regulation of PHK. These findings might explain why the in vitro PHK enzymatic activity is not deficient in XLG II, whereas it is in XLG I.
Hum Mol Genet 1996 May
PMID:X-linked liver glycogenosis type II (XLG II) is caused by mutations in PHKA2, the gene encoding the liver alpha subunit of phosphorylase kinase. 873 33

In five cases of X-linked liver glycogenosis subtype 2 (XLG2), we have identified mutations in the gene encoding the liver isoform of the phosphorylase kinase alpha subunit (PHKA2). XLG2 is a rare variant of X-linked phosphorylase kinase (Phk) deficiency of the liver. Whereas in the more common form of X-linked hepatic Phk deficiency, XLG1, the enzyme's activity is decreased both in liver and in blood cells, Phk activity in XLG2 is low in liver but normal or even enhanced in blood cells. Although missense, nonsense and splicesite mutations in the PHKA2 gene were recently identified in several cases of XLG1, no mutations have yet been described for XLG2 and a molecular explanation for the peculiar biochemical phenotype of XLG2 has been lacking. All mutations found in the present study result in non-conservative amino acid replacements of residues that are absolutely conserved between the alpha L, alpha M and beta subunits of Phk [H132P, H132Y, R186H (twice) and D299G]. Strikingly, in two pairs of cases the mutations affect the same codon. These results demonstrate that: (i) XLG2 is caused by mutations in PHKA2 and is therefore allelic with XLG1; and (ii) XLG2 mutations appear to cluster in limited sequence regions or even individual codons.
Hum Mol Genet 1996 May
PMID:Mutation hotspots in the PHKA2 gene in X-linked liver glycogenosis due to phosphorylase kinase deficiency with atypical activity in blood cells (XLG2). 873 34

To study the hysteretic properties of rabbit skeletal muscle phosphorylase kinase the method of continuous registration of the kinetics of the kinase reaction developed by us earlier has been used. It was shown that duration of the lag period on the kinetic curves is independent of the phosphorylase kinase concentration and the simultaneous presence of phosphorylase b, Ca2+, and Mg2+ is required for the complete transition of the enzyme into the activated state.
Biochem Mol Biol Int 1996 Jul
PMID:Hysteretic properties of rabbit skeletal muscle phosphorylase kinase: synergistic activation by phosphorylase b, Ca2+, and Mg2+. 884 50

We have developed a method to study the primary sequence specificities of protein kinases by using an oriented degenerate peptide library. We report here the substrate specificities of eight protein Ser/Thr kinases. All of the kinases studied selected distinct optimal substrates. The identified substrate specificities of these kinases, together with known crystal structures of protein kinase A, CDK2, Erk2, twitchin, and casein kinase I, provide a structural basis for the substrate recognition of protein Ser/Thr kinases. In particular, the specific selection of amino acids at the +1 and -3 positions to the substrate serine/threonine can be rationalized on the basis of sequences of protein kinases. The identification of optimal peptide substrates of CDK5, casein kinases I and II, NIMA, calmodulin-dependent kinases, Erk1, and phosphorylase kinase makes it possible to predict the potential in vivo targets of these kinases.
Mol Cell Biol 1996 Nov
PMID:A structural basis for substrate specificities of protein Ser/Thr kinases: primary sequence preference of casein kinases I and II, NIMA, phosphorylase kinase, calmodulin-dependent kinase II, CDK5, and Erk1. 888 77

Phosphorylase kinase from skeletal muscle is a hexadecameric enzyme with the subunit composition (alphabeta gammadelta)4 and a mass of 1.3 x 10(6) Da. The catalytic gamma subunit and the remaining regulatory subunits are packed as a tetrahedral structure composed of two elongated, opposing (alphabeta gammadelta)2 octameric lobes. We show by immunoelectron microscopy with subunit-specific monoclonal antibodies that a portion of the beta subunit occurs on the interior face of the lobes at a region of inter-lobal interactions, and that at a proximal position slightly more central and distal on the interior lobe face lies the base (residues 277 to 290) of the helical domain of the catalytic core of the gamma subunit. Activation of the kinase by a variety of means caused similar increases in the binding to the holoenzyme of the monoclonal antibodies against these two regions of the beta and gamma subunits. Moreover, monovalent fragments of the antibodies against both regions stimulated the activity of the non-activated holoenzyme. Thus, the epitopes of the beta and gamma subunits recognized by the monoclonal antibodies are structurally coupled to each other and with the activation of phosphorylase kinase. Activation of the holoenzyme apparently involves the repositioning of the base of the catalytic domain of the gamma subunit and a proximal region of the beta subunit within the identified area on the interior face of the lobes of the tetrahedral phosphorylase kinase molecule.
J Mol Biol 1997 Jan 24
PMID:Proximal regions of the catalytic gamma and regulatory beta subunits on the interior lobe face of phosphorylase kinase are structurally coupled to each other and with enzyme activation. 901 46

Glycogen storage disease due to phosphorylase kinase deficiency occurs in several variants that differ in mode of inheritance and tissue-specificity. This heterogeneity is suspected to be largely due to mutations affecting different subunits and isoforms of phosphorylase kinase. The gene of the ubiquitously expressed beta subunit, PHKB, was a candidate for involvement in autosomally transmitted phosphorylase kinase deficiency of liver and muscle. To identify such mutations, the complete PHKB coding sequence was amplified by RT-PCR of RNA isolated from blood samples of patients and analyzed by direct sequencing of PCR products. The characterization of mutations was complemented by PCR of genomic DNA. In one female and four male patients, we identified five independent nonsense mutations (Y418ter; R428ter; Y974H+E975ter; Q656ter in two cases), one single-base insertion in codon N421, one splice-site mutation affecting exon 31, and a large deletion involving the loss of exon 8. Although these severe translation-disrupting mutations occur in constitutively expressed sequences of the only known beta subunit gene of phosphorylase kinase, PHKB, they are associated with a surprisingly mild clinical phenotype, affecting virtually only the liver, and relatively high residual enzyme activity of approximately 10%.
Hum Mol Genet 1997 Jul
PMID:Autosomal glycogenosis of liver and muscle due to phosphorylase kinase deficiency is caused by mutations in the phosphorylase kinase beta subunit (PHKB). 921 82

Mutations in three different genes of phosphorylase kinase (Phk) subunits, PHKA2, PHKB and PHKG2, can give rise to glycogen storage disease of the liver. The autosomal-recessive, liver-specific variant of Phk deficiency is caused by mutations in the gene encoding the testis/liver isoform of the catalytic gamma subunit, PHKG2. To facilitate mutation detection and to improve our understanding of the molecular evolution of Phk subunit isoforms, we have determined the structure of the human PHKG2 gene. The gene extends over 9.5 kilonucleotides and is divided into 10 exons; positions of introns are highly conserved between PHKG2 and the gene of the muscle isoform of the gamma subunit, PHKG1. The beginning of intron 2 harbors a highly informative GGT/GT microsatellite repeat, the first polymorphic marker in the PHKG2 gene at human chromosome 16p11.2-p12.1. Employing the gene sequence, we have identified homozygous translation-terminating mutations, 277delC and Arg44ter, in the two published cases of liver Phk deficiency who developed cirrhosis in childhood. As liver Phk deficiency is generally a benign condition and progression to cirrhosis is very rare, this finding suggests that PHKG2 mutations are associated with an increased cirrhosis risk.
Hum Mol Genet 1998 Jan
PMID:Liver glycogenosis due to phosphorylase kinase deficiency: PHKG2 gene structure and mutations associated with cirrhosis. 938 16

Under conditions preventing the direct binding of phosphorylase kinase to glycogen, we detected the formation of the compound ternary complex of glycogen, phosphorylase and phosphorylase kinase. The complex formation occurs in two stages: (i) the formation of phosphorylase-glycogen complex controlled by ATP, (ii) the binding of phosphorylase kinase to the previously formed phosphorylase-glycogen complex exclusively in the presence of Ca2+ and Mg2+. The process is responsible for the increase of phosphorylase kinase activity in the presence of glycogen. An opinion is offered that a specific order of enzyme binding to glycogen particle as support provides for a self-assembly of the studied metabolon and plays an essential role in the regulation of glycogenolysis.
Biochem Mol Biol Int 1997 Nov
PMID:A study of supramolecular organization of glycogenolytic enzymes in vertebrate muscle tissue. 938 46

Unequal homologous recombination between repetitive genetic elements is one mechanism that mediates genome instability. We have characterized a homologous recombination event between two neighboring LINE-1 sequences in the human gene encoding the beta subunit of phosphorylase kinase (PHKB). It has lead to the deletion of 7574 nucleotides of genomic DNA including exon 8 of this gene, giving rise to glycogen storage disease through phosphorylase kinase deficiency. To our knowledge, this is the first example of a mutation due to unequal homologous recombination between LINE-1 elements. The sequence features of the recombining LINE-1 elements and of the recombination junction site, and possible reasons for the more frequent occurrence of unequal homologous recombination between Alu elements are discussed.
J Mol Biol 1998 Apr 03
PMID:Unequal homologous recombination between LINE-1 elements as a mutational mechanism in human genetic disease. 953 76


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