AJP - Cell Physiology, Vol 261, Issue 4 C691-C698, Copyright © 1991 by American Physiological Society
Muscle-specific regulation of the heme biosynthetic enzyme 5'-aminolevulinate synthase
D. A. Essig and L. A. McNabney
Division of Exercise Molecular Biology, College of Kinesiology, University of Illinois, Chicago 60680.
The induction of 5'-aminolevulinate synthase (ALV synthase) activity in
adult muscle by overload occurs in the absence of proportional changes in
its mRNA content. Complete interpretation of these findings is difficult
because little is known of the basal regulation of ALV synthase expression
in muscle. In three adult chicken muscle fiber types (n = 5 each),
differences in ALV synthase activity were correlated (r greater than or
equal to 0.89; P less than 0.05) to the activities of cytochrome oxidase
(COX) and citrate synthase (CS) and to levels of the "liver" isoform of ALV
synthase mRNA. During posthatch development, ALV synthase activity and mRNA
levels (n = 3-6 per time point) also covaried with changes in COX and CS
activity. The highest levels of ALV synthase mRNA in muscle are observed
early in myogenesis prior to induction of COX activity. The regulation of
ALV synthase is also tissue-specific because the higher basal levels of ALV
synthase activity in liver mitochondria are associated with
disproportionately less oxidative enzyme activity and less of the liver ALV
synthase isoform mRNA than in muscle.
