Glycolysis and Muscle Contraction

Analysis of muscle structure began about the middle of the last century. Microscopists reported a transverse striated appearance when muscle fibers were examined by ordinary light microscopy. With the 

The muscle fibrils are embedded in sarcoplasm, each individual fibril showing the banding pattern of the whole fiber (Bowman, 1840). Myosin could be extracted from muscle with strong salt solutions. From the altered appearance of the bands after extraction it was suggested that this protein was a major component of the A bands (Kuhne,1864 Danilewsky, 1881). The localization of myosin in the A bands and of actin in the I bands was convincingly shown by Jean Hanson and Hugh Huxley (1954-1955) in electron micrographs of transected fibers and confirmed after selective extraction to remove myosin (Hasselbach, 1953 Hanson and H.E. Huxley, 1953-1955). 

That myosin, a structural protein, also had enzyme activity as an ATPase, had been shown by Engelhardt and Ljubimova (1939-1941). ATP was now found to dissociate actomyosin producing a marked fall in viscosity the ATP was split to ADP and Pj. Contrasting properties of ATP in muscle systems were also observed. The rigor seen at postmortem occurred as ATP levels fell. The ATPase activity of myosin could be inhibited by mercurials (which block SH groups on cysteine) with ATPase blocked, ATP caused muscle fibers to relax (Weber and Portzehl, 1952). 

The discovery that ATP was not only the source of the energy required for muscle contraction but was apparently directly involved in the contractile process was an enormous stimulus to biochemists and muscle biologists. In the early 1950s attempts were made to determine if the ATP was hydrolyzed to initiate the contraction or was merely involved in the recovery process. Because of the speed with which contraction occurs, experiments had to be performed with amphibian 

Baldwin, E. (1947). Dynamic Aspects of Biochemistry. Cambridge University Press. 

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