PYRUVATE-KINASE ISOZYMIC SHIFTS OF DIFFERENTIATING CHICK MYOGENIC CELLS INVIVO AND IN CULTURE

Developing chick skeletal muscle undergoes an isozymic shift from type K pyruvate kinase to type M during development. A major increase in pyruvate kinase activity follows the isozymic shift, resulting in at least 40-fold higher specific activities by adulthood. Similar isozymic changes occur in primary cultures of myogenic cells from 12-day-old chick embryos. Cultures initially contain only type K pyruvate kinase. Type M appears by the fourth day of culture and accounts for 80-90% of the activity by the eleventh day. Type M did not accumulate when cell fusion was prevented by removing Ca2+ from the growth medium or when protein synthesis was inhibited by cycloheximide. © 1979.