Glycogen debranching enzyme is associated with rat skeletal muscle sarcoplasmic reticulum.
OBJECTIVE
Gel electrophoresis revealed a band of molecular weight approximately 160 000 Da associated with the skeletal muscle sarcoplasmic reticulum (SR) vesicle preparations. This investigation sought to examine glycogen debranching enzyme associated with skeletal muscle SR.


METHODS
Sarcoplasmic reticulum samples were also taken from muscle whose glycogen content had been reduced either via stimulation of the sciatic nerve or alpha-amylase treatment of muscle homogenates.


RESULTS
The stimulation protocol reduced whole muscle glycogen by 86% (7.4 +/- 0.4 vs. 1.0 +/- 0.3 microg mg(-1) wet mass, P < or = 0.05). Glycogen associated with the SR was reduced by 82% in the stimulation protocol (533 +/- 82 vs. 96 +/- 7 microg mg(-1) protein) and by 94% in alpha-amylase treatment (493 +/- 11 vs. 29 +/- 2 microg mg(-1) protein), respectively. Gel electrophoresis and Western blots revealed that the content of glycogen debranching enzyme was reduced by approximately 53% as a result of muscle stimulation and by approximately 46% in alpha-amylase treatment (P < or = 0.05). In addition, glycogen debranching enzyme activity was reduced by 61% in stimulated samples compared with control (20.3 +/- 1.0 vs. 8.0 +/- 1.2 nmol mg(-1) min(-1), respectively), a value consistent with reductions observed from gel electrophoresis and Western blots.


CONCLUSIONS
These results confirm that similar to glycogen phosphorylase, glycogen debranching enzyme is associated with the skeletal muscle SR and is dissociated under exercise conditions.
Lees
S J
SJ
Department of Biomedical Sciences, University of Missouri, Columbia, 65211, USA.
Chen
Y-T
YT
Williams
J H
JH
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D004558:Electric Stimulation / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005260:Female; D006003:Glycogen / Q000378:metabolism; D006004:Glycogen Debranching Enzyme System / Q000378:metabolism*; D024981:Glycogen Phosphorylase / Q000378:metabolism; D018482:Muscle, Skeletal / Q000201:enzymology*; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D012584:Sciatic Nerve / Q000502:physiology
D006004:Glycogen Debranching Enzyme System; D006003:Glycogen; D024981:Glycogen Phosphorylase