Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.27 (AMPK)
 6,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Maturation-activated protein-serine/threonine kinases were investigated in the high-speed supernatant fractions from sea-star oocytes harvested at the time of germinal vesicle breakdown. One of the major stimulated protein kinases able to phosphorylate acetyl-CoA carboxylase in these extracts was found to co-purify with a 44 kDa myelin basic protein kinase (p44mpk) that is activated with a similar time course during oocyte maturation. Purified sea-star oocyte p44mpk phosphorylated acetyl-CoA carboxylase (purified from rat liver) predominantly on serine and to a small extent on threonine. Furthermore, the phosphorylation of acetyl-CoA carboxylase occurred principally on a tryptic phosphopeptide which displayed electrophoretic and chromatographic properties very similar to those of the peptide that has previously been shown to undergo increased phosphorylation in response to insulin in rat adipocytes [Brownsey & Denton (1982) Biochem. J. 202, 77-86]. The acetyl-CoA carboxylase was phosphorylated at a similar rate and to a similar extent by casein kinase II, which was also purified from maturing sea-star oocytes. Although casein kinase II was also activated approximately 3-fold near the time of nuclear envelope breakdown, it was responsible for only a minor component of the total enhanced acetyl-CoA carboxylase kinase activity measured in the soluble extracts from maturing oocytes. Acetyl-CoA carboxylase was a relatively poor substrate for the major S6 peptide kinase activity that was also stimulated during resumption of meiosis in the oocytes. The properties of the p44mpk are reminiscent of those of a microtubule-associated protein 2 (MAP-2) kinase that is activated in response to insulin and other mitogens in mammalian cells [Ray & Sturgill (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 3753-3757; Hoshi, Nishida & Sakai (1988) J. Biol. Chem. 263, 5396-5401]. It is intriguing that several of the mammalian protein kinases that are acutely activated after mitogenic prompting of quiescent mouse fibroblasts (i.e. G0 to G1 transition), such as MAP-2 kinase, casein kinase II and S6 kinase II, have counterparts that are activated during M-phase in maturing sea star oocytes.
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PMID:Identification of a major maturation-activated acetyl-CoA carboxylase kinase in sea star oocytes as p44mpk. 167 14

We have examined the sites phosphorylated on acetyl-CoA carboxylase by three protein kinases which have been shown to inactivate the enzyme, i.e. cyclic-AMP-dependent protein kinase, acetyl-CoA carboxylase kinase-2 (ACK2, purified from rat mammary gland) and the AMP-activated protein kinase (formerly called acetyl-CoA carboxylase kinase-3, purified from rat liver). Each protein kinase phosphorylates two out of three sites (termed 1-3) which have been established by amino acid sequencing. The two sites phosphorylated by each kinase can be recovered on separate peptides, TC1 and TC2, derived by combined digestion of the native enzyme by trypsin and chymotrypsin: TC1 = Ser-2Ser(P)-Met-3Ser(P)-Gly-Leu; TC2 = Arg-Met-1Ser(P)-Phe- Cyclic-AMP-dependent protein kinase phosphorylates sites 1 and 2 exclusively, whereas the AMP-activated protein kinase phosphorylates sites 1 and 3, plus at least one other minor site. ACK2 phosphorylates site 1 and, more slowly, an unidentified site(s) within TC1. We have also established the structures of the single major phosphopeptides (T1 and C1 respectively) which are recovered by HPLC after acetyl-CoA carboxylase phosphorylated by cyclic-AMP-dependent protein kinase is digested with trypsin or chymotrypsin alone. T1 is related to TC1, and has the structure: Ser-Ser(P)-Met-Ser-Gly-Leu-His-Leu-Val-Lys. C1 is identical with TC2. We have carried out studies on the correlation of the activity of acetyl-CoA carboxylase with the occupancy of sites 1, 2 and 3 during phosphorylation by each of the three protein kinases. The results suggest that phosphorylation of site 3 is primarily responsible for the large decrease in Vmax produced by the AMP-activated protein kinase, while phosphorylation of site 1 may be primarily responsible for the increase in A0.5 for citrate and more modest depression of Vmax produced by cyclic-AMP-dependent protein kinase and ACK2. Our results emphasize that amino acid sequence information is essential in the unequivocal interpretation of data from phosphopeptide mapping experiments and allow a more complete interpretation of previous data on phosphorylation of acetyl-CoA carboxylase in intact cells. They also open the way to experiments which could establish the physiological roles of these protein kinases in the control of fatty acid synthesis.
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PMID:Identification by amino acid sequencing of three major regulatory phosphorylation sites on rat acetyl-CoA carboxylase. 290 Jan 38

Acetyl-CoA carboxylase has been purified from lactating rat mammary gland using a combination of ammonium sulphate and poly(ethyleneglycol) precipitations. The enzyme was purified from 35--70-fold with a yield of over 50%, the exact figures being difficult to estimate because of activation of the enzyme that occurs during the preparation. The preparation was homogeneous by the criterion of polyacrylamide gel electrophoresis in sodium dodecyl sulphate and had a single subunit of molecular weight 240,000, containing 1.02 +/- 0.04 molecules of biotin and 3.1 +/- 1.7 molecules of alkali-labile phosphate per subunit. The purified enzyme was phosphorylated and inactivated rapidly when incubated in the presence of [gamma 32P]ATP and magnesium ions with the purified catalytic subunit of cyclic-AMP-dependent protein kinase from rabbit skeletal muscle. Both phosphorylation and inactivation are blocked by the heat-stable protein inhibitor of cyclic-AMP-dependent protein kinase, and can be reversed by incubation with purified protein phosphatase-1 from rabbit skeletal muscle. The inactivation by the protein kinase and reactivation by the protein phosphatase correlate with the near-stoichiometric phosphorylation and dephosphorylation of site(s) located in a single tryptic peptide. Phosphorylation does not affect the Km for substrates, but brings about a twofold decrease in V and a twofold increase in the apparent dissociation constant for the allosteric activator, citrate. We also present evidence that the activation of rabbit mammary acetyl-CoA carboxylase by protein phosphatase-1 described previously [Hardie and Cohen (1979) FEBS Lett. 103, 333-338] is due to dephosphorylation at site(s) which are not phosphorylated by either cyclic-AMP-dependent protein kinase or acetyl-CoA carboxylase kinase-2. These results suggest that the rapid inactivation of acetyl-CoA carboxylase, and hence fatty acid synthesis, by adrenaline in adipose tissue, or glucagon in the liver, is due to phosphorylation of the enzyme by cyclic-AMP-dependent protein kinase.
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PMID:Reversible phosphorylation and inactivation of acetyl-CoA carboxylase from lactating rat mammary gland by cyclic AMP-dependent protein kinase. 610 9

Three cyclic AMP-independent acetyl-CoA carboxylase kinases (A, B1 and B2) have been isolated from lactating rat mammary gland, using phosphocellulose chromatography, high performance gel filtration, and affinity chromatography on casein-Sepharose and phosvitin-Sepharose. These protein kinases have been identified with previously described kinases by the following criteria. Kinase A phosphorylates the same sites on rabbit mammary acetyl-CoA carboxylase as acetyl-CoA carboxylase kinase 2, which was originally described as a contaminant of rabbit mammary acetyl-CoA carboxylase purified by the poly(ethylene glycol)procedure. Kinase A will henceforth be referred to as acetyl-CoA carboxylase kinase-2. Kinase B1 has been identified with casein kinase II by its heparin sensitivity, elution behaviour on phosphocellulose, molecular mass, substrate specificity and subunit composition. Kinase B2 has been identified with casein kinase I by its elution behaviour on phosphocellulose, molecular mass, substrate specificity and subunit composition. The three kinases phosphorylate distinct sites on acetyl-CoA carboxylase. Phosphorylation by either casein kinase I or II does not affect enzyme activity. However, acetyl-CoA carboxylase kinase 2 inactivates acetyl-CoA carboxylase reversibly, in an identical manner to cyclic-AMP-dependent protein kinase, and phosphorylates sites located on identical peptides. Acetyl-CoA carboxylase kinase-2 can, however, be distinguished from the free catalytic subunit of cyclic-AMP-dependent protein kinase by its molecular mass, its substrate specificity, its elution behaviour on phosphocellulose, and its complete lack of sensitivity to the protein inhibitor of cyclic-AMP-dependent protein kinase. We also present evidence that phosphorylation of acetyl-CoA carboxylase by cyclic-AMP-dependent protein kinase occurs directly and not via a bicyclic cascade system as proposed by other laboratories.
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PMID:Isolation of three cyclic-AMP-independent acetyl-CoA carboxylase kinases from lactating rat mammary gland and characterization of their effects on enzyme activity. 614 23

The catalytic subunit of cyclic AMP-dependent protein kinase stimulates the inactivation of acetyl-coenzyme A (CoA) carboxylase by acetyl-CoA carboxylase kinase. The stimulated inactivation of carboxylase is due to activation of carboxylase kinase by the catalytic subunit. Activation of carboxylase kinase activity is accompanied by the incorporation of 0.6 mol of phosphate per mole of carboxylase kinase. Addition of the regulatory subunit of cyclic AMP-dependent protein kinase prevents the activation of carboxylase kinase. Phosphorylation and activation of carboxylase kinase has no effect on the Km for ATP, but decreases the Km for acetyl-CoA carboxylase from 93 to 45 nM. Inactivation of carboxylase by the carboxylase kinase requires the presence of coenzyme A even when the activated carboxylase kinase is used. Acetyl-CoA carboxylase is not phosphorylated or inactivated by the catalytic subunit of cyclic AMP-dependent protein kinase.
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PMID:Phosphorylation and activation of acetyl-coenzyme A Carboxylase kinase by the catalytic subunit of cyclic AMP-dependent protein kinase. 631 99

An insulin-stimulated protein kinase specific for acetyl-CoA carboxylase has been purified from rat epididymal adipose tissue using Mono-Q chromatography. The kinase binds to (and phosphorylates) the relatively inactive, dimeric form of acetyl-CoA carboxylase, but not to its active, polymeric form, and this property has been used to purify the kinase. Under the conditions used, phosphorylation by the purified kinase did not result in a detectable increase in acetyl-CoA carboxylase activity. These studies also led to the recognition of an 'activator' protein which is capable of increasing the activity of acetyl-CoA carboxylase without changing its phosphorylation state. It is suggested that this 'activator' protein, together with the insulin-activated acetyl-CoA carboxylase kinase, may play a role in the activation of acetyl-CoA carboxylase by insulin.
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PMID:Purification and characterisation of an insulin-stimulated protein-serine kinase which phosphorylates acetyl-CoA carboxylase. 947 66

C4 photosynthesis is functionally dependent on metabolic interactions between mesophyll and bundle-sheath cells. Although the C4 cycle is biochemically well understood many aspects of the regulation of enzyme activities, gene expression and cell differentiation are elusive. Protein kinases are likely involved in these regulatory processes providing links to hormonal, metabolic and developmental signal transduction pathways. We have identified several protein kinases that are differentially expressed in mesophyll and bundle-sheath cells of the C4 plant Sorghum bicolor. Here we describe the characterization of two putative protein kinases that show high similarity to the SNF1/AMPK family of protein serine/threonine kinases. The mRNA of both kinases accumulates to much higher levels in mesophyll cells than in the bundle-sheath and can also be detected in root tissue. Complementation experiments with a snf1 mutant of Saccharomyces cerevisiae indicate that the S. bicolor protein kinase SNFL1 does not represent a functional homologue of the yeast SNF1 protein kinase.
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PMID:Characterization of a Sorghum bicolor gene family encoding putative protein kinases with a high similarity to the yeast SNF1 protein kinase. 948 48

Here we report that the beta-adrenergic agonist isoproterenol increases the activity of the stress-activated kinase p38 MAPK over 10-fold in freshly isolated rat epididymal fat cells. Stimulation of the kinase was rapid, sustained for at least 60 min and sensitive to the specific p38 MAPK inhibitor, SB 203580. Half-maximal stimulation of p38 MAPK by isoproterenol occurred at 13 nM isoproterenol. The cell permeable cyclic AMP analogue, chlorophenylthio-cyclic AMP increased p38 MAPK activity to a similar extent to isoproterenol, suggesting that the effect of the beta-adrenergic agonist is mediated via increases in the activity of cyclic-AMP dependent protein kinase. Although it had little or no effect on the activity of c-Jun N-terminal kinase, isoproterenol and a number of other treatments which activated p38 MAPK were found to stimulate AMP-activated protein kinase in fat cells. Activation of AMPK and p38 MAPK were not, however, found to be directly linked.
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PMID:The activation of p38 MAPK by the beta-adrenergic agonist isoproterenol in rat epididymal fat cells. 984 39

We have isolated five cDNA clones (osk1-5) for protein kinases from rice which are related to SNF1 protein kinase of Saccharomyces cerevisiae. Based on the sequence homology, these cDNAs can be classified into two groups, group 1 (osk1) and group 2 (osk2-5). The products of these genes were demonstrated to be functional SNF1-related protein kinases by in vitro and in vivo experiments. Recombinant proteins expressed from both groups of genes were fully active as protein kinases and could phosphorylate SAMS peptide, a substrate specific for the SNF1/AMPK family, as well as themselves (autophosphorylation). Moreover, expression of osk3 cDNA in yeast snf1 mutants restored SNF1 function. Northern blot analyses showed differential expression of these two gene groups; group 1 is expressed uniformly in growing tissues (young roots, young shoots, flowers, and immature seeds), whereas group 2 is strongly expressed in immature seeds. SNF1-related protein kinases have been reported from different plant species, such as rye, barley, Arabidopsis, tobacco, and potato, while the type of gene strongly expressed in immature seeds is known only in cereals such as rye, barley, and, from our findings, in rice. Expression levels of the group 2 genes were further analyzed in seeds during seed maturation. Expression is transiently increased in the early stages of seed maturation and then decreases. The expression peak precedes those of the sbe1 and waxy genes, which are involved in starch synthesis in rice. Taken together, these findings suggest that group 2 OSK genes play important roles in the early stages of endosperm development in rice seeds.
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PMID:Rice has two distinct classes of protein kinase genes related to SNF1 of Saccharomyces cerevisiae, which are differently regulated in early seed development. 987 Jul 4

StubSNF1 is a potato cDNA that encodes a protein kinase similar to the yeast SNF1 gene involved in transcriptional regulation of glucose-repressible genes. The yeast SNF1 functions in a complex with GAL83/SIP1/SIP2 and SNF4 proteins. We have used StubSNF1 as bait in a yeast two-hybrid system to screen for potato cDNAs encoding proteins that bind to StubSNF1. Three overlapping cDNAs, two different in size, were isolated. DNA sequence analysis revealed that they were orthologues of the yeast GAL83/SIP1/SIP2 genes and their mammalian counterparts, AMPK beta-subunits. The direct interaction between the potato proteins StubGAL83 and StubSNF1 was shown by an in vitro binding assay. Southern and Northern hybridisations revealed that StubGAL83 exists in a low copy number in the potato genome and is highly (but organ-specifically) expressed in potato. In contrast, StubSNF1 possesses low transcript levels in each organ, except in flowers where high amounts of StubSNF1 mRNA could be detected. We demonstrate here that StubGAL83 can also interact with yeast SNF4 in a yeast two-hybrid system suggesting that plant SNF1 kinases may function in complexes similar to those detected in yeast and mammals.
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PMID:Potato StubSNF1 interacts with StubGAL83: a plant protein kinase complex with yeast and mammalian counterparts. 1020 10


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