Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.3.1 (citrate synthase)
 4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Muscle fiber types are classified based on contractile speed and type of metabolism. Fast-contracting fibers involve mainly glycolytic-based metabolism, whereas slow-contracting fibers involve a more oxidative type of energy metabolism. The relationship between expression of the genes controlling these functional characteristics and their relative protein abundance in porcine muscle is unknown. The objective of this study was to determine the expression of adult myosin heavy-chain (MyHC) genes and their corresponding protein content in various porcine muscles. Moreover, changes in expression of 2 genes involved in energy metabolism (glycogen synthase and citrate synthase) were determined on muscles varying in MyHC. Using real-time PCR, the relative transcript abundance was determined for the adult MyHC isoforms (types I, IIA, IIX, and IIB), glycogen synthase, and citrate synthase in the masseter (MAS), diaphragm, longissimus, cutaneous trunci, and red and white semitendinosus muscles of 7 pigs. Each muscle was subjected to SDS-PAGE analyses to determine the relative abundance of each MyHC. The relative transcript abundance of type IIB MyHC was greatest (P < 0.05) in the longissimus, white semitendinosus, and cutaneous trunci muscles, whereas type I MyHC expression was greatest (P < 0.05) in the MAS, diaphragm, and red semitendinosus muscles. Glycogen synthase gene expression was least in the MAS (P < 0.01) but exhibited a pattern similar to MyHC IIB expression across muscles. Citrate synthase transcript abundance, however, varied (P < 0.05) independently of MyHC gene expression. Expression of types I and IIB MyHC was correlated with their tissue protein content (R2 = 0.76 and 0.78, respectively), whereas type IIA and X MyHC expression did not correlate with the SDS-PAGE-determined protein content. These data show differences in MyHC gene expression across various porcine muscles and suggest that expression of these genes is reflective of the type of myosin contained within the muscle. Moreover, these data show that expression of energy-specific genes differs greatly across porcine muscles with different functions.
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PMID:Contractile protein content reflects myosin heavy-chain isoform gene expression. 1714 75

The dominant RN mutation in pigs results in excessive glycogen storage in skeletal muscle. The mutation is situated in the PRKAG3 gene, which encodes a muscle-specific isoform of the AMP-activated protein kinase (AMPK) gamma3 subunit. AMPK is an important regulator of carbohydrate and fat metabolism in mammalian cells. The aim of the present study was to examine the effect of exercise on glycogen synthesis signalling pathways in muscle and to study enzyme activities of importance in carbohydrate metabolism in pigs with or without the PRKAG3 mutation. Glycogen content, metabolic enzyme activities and expression or phosphorylation of signalling proteins were analysed in skeletal muscle specimens obtained at rest, after a single treadmill exercise bout and after 3 h recovery. The PRKAG3 mutation carriers had higher glycogen content, a tendency for lower expression of AMPK (P < 0.07) and higher hexokinase and phosphorylase activities, whereas citrate synthase, 3-hydroxyacyl-CoA dehydrogenase and glycogen synthase activities did not differ between genotypes. Carriers and non-carriers of the RN mutation showed a similar degradation of glycogen after exercise, whereas the rate of resynthesis was faster in the carriers. Acute exercise stimulated Akt phosphorylation on Ser(473) in both genotypes, and the effect was greater in the carriers than in the non-carriers. Acute exercise also stimulated phosphorylation of Akt substrate of 160 kDA and Glycogen synthase kinase 3 in the carriers and GSK3alpha in the non-carriers. In conclusion, the increased rate of glycogen synthesis following exercise in pigs carrying the PRKAG3 mutation correlates with an increased signalling response of Akt and its substrate, AS160, and a higher activity of hexokinase, indicating an increased glucose influx and phosphorylation of glucose, directed towards glycogen synthesis.
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PMID:Effects of exercise on muscle glycogen synthesis signalling and enzyme activities in pigs carrying the PRKAG3 mutation. 2002 49