A putative pathway of glyconeogenesis in skeletal muscle.
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, but 14C-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, decreased 14C-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.
D000409:Alanine / Q000378:metabolism; D000818:Animals; D003964:Diaphragm; D006003:Glycogen / Q000096:biosynthesis*; D007532:Isoleucine / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D007532:Isoleucine; D006003:Glycogen; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D000409:Alanine