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[Glycogen metabolic enzymes in the skeletal muscles of the developing chick embryo]
Insights
Chick embryo skeletal muscle phosphorylase (EC. 2.4.1.1) shows dynamic isozyme changes during development. Enzyme activity significantly increases, indicating crucial roles in muscle maturation.
Area of Science:
- Biochemistry
- Developmental Biology
- Muscle Physiology
Background:
- Skeletal muscle development involves complex enzymatic regulation.
- Phosphorylase (EC. 2.4.1.1) and glycogen synthetase (EC. 2.4.1.11) are key enzymes in glycogen metabolism.
- Isozymes play distinct roles in cellular processes.
Purpose of the Study:
- To investigate the ontogeny of phosphorylase isozymes in chick embryo skeletal muscle.
- To characterize the changes in phosphorylase and glycogen synthetase activity during embryogenesis.
- To understand the developmental regulation of glycogen metabolism in muscle.
Main Methods:
- Electrophoresis to separate and identify phosphorylase isozymes.
- Immunochemical analysis to differentiate isozyme characteristics.
- Enzyme activity assays for phosphorylase and glycogen synthetase.
Main Results:
- Two phosphorylase isozymes are present in chick embryo skeletal muscle (days 10-15), one similar to liver phosphorylase and another to adult rat skeletal muscle phosphorylase.
- From day 17 onwards, a single adult bird skeletal muscle-type phosphorylase isozyme predominates.
- A distinct embryonic isozyme, different from adult forms, is found in the whole 4-day-old embryo.
- Phosphorylase activity in skeletal muscle increases over 50-fold from day 10 to hatching, while glycogen synthetase activity increases only 4-fold.
Conclusions:
- Chick embryo skeletal muscle phosphorylase undergoes significant isozyme transitions during development.
- The marked increase in phosphorylase activity suggests a critical role in muscle maturation and glycogen breakdown.
- Differential regulation of phosphorylase and glycogen synthetase points to specific metabolic adaptations during embryogenesis.
Abstract:
In the skeletal muscles of the chick embryo from the 10th till the 15th day of embryogenesis, phosphorylase (EC. 2.4.1.1) is represented by two isozymes one of which corresponds, by electrophoretic mobility, to the liver phosphorylase and another to phosphorylase of the skeletal muscles of the adult rat. From the 17th day of embryogenesis on only one isozyme of phosphorylase is found in the skeletal muscles which is identical with that of the skeletal muscles of the adult bird. The isozyme spectrum of phosphorylase of the whole 4 days old embryo contains, besides phosphorylase L, a special "embryonic" isozyme which differs from that of the skeletal muscles by immunochemical characteristics and electrophoretic mobility. From the 10th day of embryogenesis till hatching, the activity of phosphorylase of the skeletal muscles increases more than 50 times and that of glycogen synthetase (EC. 2.4.1.11) only 4 times.