A putative pathway of glyconeogenesis in skeletal muscle |
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Authors: | Bhanu R. Odedra T. Norman Palmer |
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Affiliation: | (1) Department of Biochemistry, Charing Cross Hospital Medical School, Fulham Palace Road, W6 8RF London, UK;(2) Present address: Clinical Nutrition and Metabolism Unit, London School of Hygiene and Tropical Medicine, Hospital for Tropical Diseases, 4 St. Pancras Way, NW1 2PE London, UK |
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Abstract: | Evidence is presented in support of a pathway in skeletal muscle of glyconeogenesis (glycogen biosynthesis de novo) from L-glutamate and related amino acids involving the enzyme phosphoenolpyruvate carboxykinase (PEP CK). In the rat hemidiaphragm in vitro, not only did L-[U-14C]glutamate exert a glycogen-sparing action, but14C-label was incorporated into glycogen. The incorporation is thought not to be simply via label randomization and was decreased by factors that increased glycolysis or pyruvate oxidation. 3-Mercaptopicolinate and amino-oxyacetate, specific inhibitors of PEP CK and aminotransferase-type enzymes, respectively, decreased14C-incorporation from L-[U-14C]glutamate into glycogen. No quantitative determination of apparent glyconeogenic flux was made, and it remains to be established whether glyconeogenesis via PEP CK and/or via PEP CK coupled with 'malic' enzyme (or pyruvate carboxylase) is functionally important in skeletal muscle. |
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