A study of the adenosinetriphosphatase activity of developing chick muscle

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Abstract
Muscle extracts containing the sarcoplasmic and myofibrillar proteins were prepared in 0.6 [image] KCl-borate soln. and the myofibrillar proteins precipitated on dilution to 0.05 [image] KC1. In the adult most of the muscle adenosinetriphosphatase is present in the precipitate in association with the protein, myosin. The adenosinetriphosphatase activity of the whole extract and of the precipitate was determined at different developmental stages. In the earliest embryos studied the percentage of the total activity in the sarcoplasmic fraction is high in comparison with that in the myofibrillar protein fraction alone. As development proceeds the distr. changes and the enzyme becomes more closely associated with the myofibril. The adenosinetriphosphatase activity of the sarcoplasmic fraction was studied in water extracts of embryonic muscle. Its relation to the adult myosin adenosinetriphosphatase and to that associated with the cell particulate systems of muscle was considered. The work cannot be related to previous studies on the protein distr. in chick muscle since the methods of prepn. of the fractions are different. Some possible interpretations of the results are discussed.