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

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Query: EC:6.4.1.2 (acetyl-CoA carboxylase)
2,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protein phosphorylation is well established as a regulatory mechanism in higher plants, but only a handful of plant enzymes are known to be regulated in this manner, and relatively few plant protein kinases have been characterized. AMP-activated protein kinase regulates key enzymes of mammalian fatty acid, sterol and isoprenoid metabolism, including 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. We now show that there is an activity in higher plants which, by functional criteria, is a homologue of the AMP-activated protein kinase, although it is not regulated by AMP. The plant kinase inactivates mammalian HMG-CoA reductase and acetyl-CoA carboxylase, and peptide mapping suggests that it phosphorylates the same sites on these proteins as the mammalian kinase. However, with the target enzymes purified from plant sources, it inactivates HMG-CoA reductase but not acetyl-CoA carboxylase. The kinase is located in the soluble, and not the chloroplast, fraction of leaf cells, consistent with the idea that it regulates HMG-CoA reductase, and hence isoprenoid biosynthesis, in vivo. The plant kinase also appears to be part of a protein kinase cascade which has been highly conserved during evolution, since the kinase is inactivated and reactivated by mammalian protein phosphatases (2A or 2C) and mammalian kinase kinase, respectively. This contrasts with the situation for many other mammalian protein kinases involved in signal transduction, which appear to have no close homologue in higher plants. To our knowledge, this represents the first direct evidence for a protein kinase cascade in higher plants.
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PMID:Evidence for a protein kinase cascade in higher plants. 3-Hydroxy-3-methylglutaryl-CoA reductase kinase. 135 11

Adrenalin and glucagon inhibit glycogen, fatty acid and cholesterol synthesis by elevation of cyclic AMP, activation of cyclic AMP-dependent protein kinase and increased phosphorylation of the rate-limiting enzymes of these pathways. Here, we review recent evidence which indicates that inhibition of these biosynthetic pathways in muscle, adipose tissue and liver is much more indirect than has previously been supposed. In particular, cyclic AMP-dependent protein kinase does not appear to inhibit glycogen synthase, acetyl-CoA carboxylase and HMG-CoA reductase by phosphorylating them directly. It appears to achieve the same end result by inactivation of the protein phosphatases which dephosphorylate these regulatory enzymes in vivo, although this has only been established definitively in the case of glycogen synthesis.
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PMID:The actions of cyclic AMP on biosynthetic processes are mediated indirectly by cyclic AMP-dependent protein kinase. 165 40

In addition to acetyl-CoA carboxylase and HMG-CoA reductase, the AMP-activated protein kinase phosphorylates glycogen synthase, phosphorylase kinase, hormone-sensitive lipase and casein. A number of other substrates for the cyclic AMP-dependent protein kinase, e.g., L-pyruvate kinase and 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase, are not phosphorylated at significant rates. Examination of the sites phosphorylated on acetyl-CoA carboxylase, hormone-sensitive lipase, glycogen synthase and phosphorylase kinase suggests a consensus recognition sequence in which the serine residue phosphorylated by the AMP-activated protein kinase has a hydrophobic residue on the N-terminal side (i.e., at -1) and at least one arginine residue at -2, -3 or -4. Substrates for cyclic AMP-dependent protein kinase which lack the hydrophobic residue at -1 are not substrates for the AMP-activated protein kinase.
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PMID:The substrate and sequence specificity of the AMP-activated protein kinase. Phosphorylation of glycogen synthase and phosphorylase kinase. 256 85

Changes in the activities of acetyl-CoA carboxylase and HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase were studied in primary cultures of adult-rat hepatocytes after exposure of the cells to insulin and/or carbohydrates. To determine the contribution of protein synthesis to changes in enzyme activity, the relative rate of synthesis of each enzyme was measured and the amount of translatable mRNA coding for the enzymes was determined by translation in vitro and immunoprecipitation. Addition of insulin to the culture medium increased the activities of acetyl-CoA carboxylase and HMG-CoA reductase by approx. 4- and 3-fold respectively. Although similar increases in the relative rate of synthesis of each protein and template activity were noted, initial increases in the activity of each enzyme occurred before any changes in protein synthesis were observed, suggesting the involvement of post-translational modification of enzyme activity in addition to changes in protein synthesis. The addition of fructose to the culture medium, in the absence of insulin, increased the activity of the carboxylase and the reductase approx. 3-fold, similar to the effects of insulin. However, the effect of fructose was to increase the rate of synthesis and the amount of translatable mRNA coding for acetyl-CoA carboxylase, whereas the increase in the activity of HMG-CoA reductase was not accompanied by any changes in the rate of synthesis or template activity. The effects of fructose could not be mimicked by glucose unless insulin was also present in the culture medium. Similar to observations in vitro, the injection of insulin or the feeding of a high-fructose diet to rats made diabetic by the injection of streptozotocin produced an increase in the activities of acetyl-CoA carboxylase and HMG-CoA reductase, and only the increase in the activity of the carboxylase was accompanied by an increase in the amount of translatable mRNA coding for the enzyme. The results are discussed in terms of the effects of fructose on the synthesis of enzymes involved in lipogenesis.
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PMID:Role of protein synthesis in the carbohydrate-induced changes in the activities of acetyl-CoA carboxylase and hydroxymethylglutaryl-CoA reductase in cultured rat hepatocytes. 286 Aug 99

The effect of cholesterol diet on the rate of mevalonic acid biosynthesis from 1-14C acetyl-CoA, 2-14C malonyl-CoA and the incorporation of these substrates into sterols and bile acids in rabbit liver were studied. Simultaneously, the activities of 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) and acetyl-CoA carboxylase and the biosynthesis of fatty acids from acetyl-CoA and malonyl-CoA were measured. Hypercholesterolemia was found to be concomitant with the inhibition of acetyl-CoA carboxylase activity only in cell-free (700 g) and mitochondrial fractions and slightly decreased the incorporation of acetyl-CoA and malonyl-CoA into fatty acids in the postmitochondrial fraction. The HMG-CoA reductase activity in all subcellular fractions except for the postmicrosomal one was inhibited under these conditions. A significant decrease of acetyl-CoA incorporation and an increase in malonyl-CoA incorporation into mevalonic acid in all liver fractions except for microsomal one were observed in rabbits with hypercholesterolemia. These data provide evidence for the existence of two pathways of mevalonic acid synthesis from the above-said substrates that are differently sensitive to cholesterol. Cholesterol feeding resulted in a decreased synthesis of the total unsaponified fraction including cholesterol from acetyl-CoA, malonyl-CoA and mevalonic acid. The rate of incorporation of these substrates into lanosterol was unchanged. All the indicated substrates (acetyl-CoA, malonyl-CoA, mevalonic acid) are precursors of bile acid synthesis in rabbit liver. Cholesterol feeding and the subsequent development of hypercholesterolemia resulted in bile acid synthesis stimulation, preferentially in the formation of the cholic + deoxycholic acids from these precursors.
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PMID:[Formation of mevalonic acid, sterols and bile acids from [1-14C]acetyl-CoA and [2-14C]malonyl-CoA in the liver of rabbits with experimental hypercholesterolemia]. 288 84

A highly purified rat liver protein kinase phosphorylates and inactivates acetyl-CoA carboxylase, and causes rapid inactivation of microsomal HMG-CoA reductase in the presence of MgATP. Both effects are stimulated in an identical manner by AMP, and are greatly reduced by prior treatment of the kinase with purified protein phosphatase. The dephosphorylated kinase can be reactivated in the presence of MgATP, apparently due to a distinct kinase kinase, and this reactivation is stimulated by nanomolar concentrations of palmitoyl-CoA. These results show that a common, bicyclic protein kinase cascade can potently inactivate the regulatory enzymes of both fatty acid and cholesterol biosynthesis.
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PMID:A common bicyclic protein kinase cascade inactivates the regulatory enzymes of fatty acid and cholesterol biosynthesis. 2462 16

The activities of acetyl-CoA carboxylase (EC 6.4.1.2), fatty acid synthetase (FAS) and beta-hydroxy-beta-methylglutaryl-CoA (HMG-CoA) reductase (EC 1.1.1.88) were determined in subcellular fractions of livers from chicks fed different cereal-based diets. With a barley-based diet as compared to corn, the following was observed: body and liver weights decreased 31%; HMG-CoA reductase activity of liver decreased 79%; acetyl-CoA carboxylase activity increased 3-fold; fatty acid synthesis increased 5-fold, and plasma and liver cholesterol decreased 45% and 35%, respectively. The suppression and induction of activities of the two divergent pathways (cholesterol and fatty acid biosynthesis) persisted for at least 21 days. Wheat, oats and rye showed a similar but less pronounced effect. The pronounced decrease in plasma cholesterol level and HMG-CoA reductase activity have implications for human nutrition and possible control of the cardiovascular diseases in which cholesterol plays a key role.
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PMID:Regulation of lipid metabolism in chicken liver by dietary cereals. 610 15

Administration of estradiol-17 beta to male Xenopus laevis evokes the proliferation of the endoplasmic reticulum and the Golgi apparatus and the synthesis and secretion by the liver of massive amounts of the egg yolk precursor phospholipoglycoprotein, vitellogenin. We have investigated the effects of estrogen on three key regulatory enzymes in lipid biosynthesis, 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase, the major regulatory enzyme in cholesterol and isoprenoid synthesis, and acetyl-CoA carboxylase and fatty acid synthetase, which regulate fatty acid biosynthesis. HMG-CoA reductase activity and cholesterol synthesis increase in parallel following estrogen administration. Reductase activity in estrogen stimulated Xenopus liver cells peaks at 40-100 times the activity observed in control liver cells. The increased rate of reduction of HMG-CoA to mevalonic acid is not due to activation of pre-existing HMG-CoA reductase by dephosphorylation, as the fold induction is unchanged when reductase from control and estrogen-stimulated animals is fully activated prior to assay. The estrogen-induced increase of fatty acid synthesis is paralleled by a 16- to 20-fold increase of acetyl-CoA carboxylase activity, indicating that estrogen regulates fatty acid synthesis at the level of acetyl-CoA carboxylase. Fatty acid synthetase activity was unchanged during the induction of fatty acid biosynthesis by estrogen. The induction of HMG-CoA reductase and of acetyl-CoA carboxylase by estradiol-17 beta provides a useful model for regulation of these enzymes by steroid hormones.
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PMID:Estrogen regulation of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase and acetyl-CoA carboxylase in xenopus laevis. 611 Jun 64

The activity of 3-hydrosy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) and the rate of mevalonic acid (MVA) synthesis from [I-14C]acetyl-CoA and [2-14C]malonyl-CoA in the soluble (X140000 g) and microsomal fractions of rat liver and in a reconstituted system containing the soluble and microsomal fractions were studied. The changes in the activity of HMG-CoA reductase and the rate of MVA biosynthesis in the fractions at different times of the day were analyzed. The daily rhythms of the rate of acetyl-CoA and malonyl-CoA incorporation into squalene, sterols and fatty acids in the postmitochondrial fraction and the daily changes in the acetyl-CoA carboxylase activity of the soluble fraction of rat liver were compared. The incorporation of labelled acetyl-CoA and malonyl-CoA into MVA showed that the latter can be synthesized from these two substrates both in the soluble and microsomal fractions. Malonyl-CoA is a preferable substrate for MVA synthesis in the soluble fraction. MVA synthesis from acetyl-CoA proceeds fastr in the intact and solubilized microsomes than in the soluble fraction. The activity of HMG-CoA reductase was found in the soluble and microsomal fractions in practically equal amounts. The enzyme activity was increased in the microsomal fraction after its solubilization. The rate of MVA biosynthesis from acetyl-CoA and the activity of HMG-CoA reductase in the soluble fraction are practically unaffected by day-to-night changes. The activity of HMG-CoA reductase and MVA biosynthesis from acetyl-CoA in the intact and solubilized microsomal fractions reached their maximal values in the middle of the dark period. The rate of MVA biosynthesis from malonyl-CoA was decreased in the middle of the dark period in all fractions studied and reached its maximum in the middle of the light period. The daily rhythms of the acetyl-CoA carboxylase activity in the soluble fraction and the rate of MVA biosynthesis from malonyl-CoA in all fractions show a coincidence. a comparison of incorporation by the postmitochondrial fractions of acetyl-CoA and malonyl-CoA into the total non-saponified lipid fraction and its components, e. g. squalene, lanosterol and cholesterol, as well as into sterols precipitated by digitonin, showed that malonyl-CoA incorporation into the total non-saponified lipid fraction was more intensive than that of acetyl-CoA. However, acetyl-CoA was far more efficiently incorporated into sterols precipitated by digitonin or isolated by TLC than malonyl-CoA. The rate of acetyl-CoA incorporation into the total non-saponified lipid fraction and into squalene, lanosterol and cholesterol was maximal in the middle of the dark period and minimal in the middle of the light period. On the contrary, the rate of malonyl-CoA incorporation into these products was minimal in the middle of the dark period and maximal in the middle of the light period. The rate of fatty acid biosynthesis from acetyl-CoA was increased in the middle of the light and dark periods...
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PMID:[Activities of 3-hydroxy-3-methylglutaryl-CoA reductase and acetyl-CoA carboxylase and rate of biosynthesis of mevalonic acid, squalene, sterols and fatty acids from [1-14C]acetyl-CoA and [2-14C]malonyl-CoA in rat liver: changes induced by daily rhythm]. 611 51

The effects of Triton WR 1339, starvation and cholesterol diet on the activities of 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) and acetyl-CoA carboxylase and on the rates of mevalonic acid (MVA) biosynthesis from acetyl-CoA and malonyl-CoA in the soluble (140 000 g) and microsomal fractions of rat liver, on the rate of incorporation of these substrates into squalene, cholesterol and lanosterol in the rat liver postmitochondrial fraction and on the rate of fatty acid biosynthesis was studied. The administration of Triton WR 1339 (200 mg per 100 g of body weight twice) stimulated the activity of HMG-CoA reductase and MVA biosynthesis from acetyl-CoA and malonyl-CoA in the intact and solubilized microsomal fractions and had no effect on these parameters in the soluble fraction. Starvation for 36 hrs did not cause inhibition of the reductase activity or MVA biosynthesis from both substrates in the soluble fraction. Alimentary cholesterol significantly increased the activity of HMG-CoA reductase, had no effect on the rate of MVA biosynthesis from acetyl-CoA and stimulated the malonyl-CoA incorporation in to MVA in the soluble fraction. Starvation an alimentary cholesterol inhibited the HMG-CoA reductase activity and MVA biosynthesis from both substrates in the solubilized microsomal fraction. Triton WR 1339 stimulated 4--19-fold the lipid formation in the total unsaponified fraction and its components i.e. squalene, lanosterol, cholesterol, from acetyl-CoA and only insignificantly (1,2--1,7-fold) increased malonyl-CoA incorporation into these compounds. Starvation and alimentary cholesterol repressed lanosterol and cholesterol biosynthesis from acetyl-CoA, decreased malonyl-CoA incorporation into these sterols and had no influence on squalene biosynthesis from the two substrates. Triton WR 1339 and starvation inhibited the acetyl-CoA carboxylase activity, unaffected by alimentary cholesterol. No significant changes in the rate of fatty acid biosynthesis from the substrates were observed. The data obtained provide evidence for the existence of autonomic pathways of MVA biosynthesis localized in the soluble and microsomal fractions of rat liver. The pathway of MVA biosynthesis in the soluble fraction is less sensitive to regulatory factors. Sterol biosynthesis from malonyl-CoA is also more resistant to regulatory effects than sterol biosynthesis from acetyl-CoA. This suggests that HMG-CoA reductase localized in the soluble fraction takes part in MVA and sterol biosynthesis from malonyl-CoA.
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PMID:[Activities of 3-hydroxyl-3-methylglutaryl-CoA reductase and acetyl-CoA carboxylase and the rate of mevalonic acid, squalene, sterol and fatty acid biosynthesis from [1-14C]acetyl-CoA and [2-14C]malonyl-CoA in rat liver: effects of Triton WR 1339, starvation and cholesterol diet]. 611 54


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