Myosin of fast and slow muscles of the rabbit
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TL;DR
Myosin of slow muscles of the rabbit has two or three times lower actin-activated and EDTA-activated ATPase and Ca++-activatedATPase and ITPase activities than those of rabbit fast muscles.
Abstract
Myosin of slow muscles of the rabbit has two or three times lower actin-activated and EDTA-activated ATPase and Ca++-activated ATPase and ITPase activities than those of rabbit fast muscles. Unlike myosin of fast muscles, the Ca++- and EDTA-activated ATPase activities of myosin of slow muscles are not increased in the alkaline pH range. Despite these qualitative differences, both kinds of muscle contain the same amount of myosin. Fast muscle contains more sarcoplasmic and less stroma proteins than slow muscle, whereas actin content is the same. After 19 days of denervation the myosin isolated from fast muscle shows only a slight decrease in its NTPase activities and no change in its pH-activity curve compared with the myosin of the same normal muscle.