Respiratory granules of heart muscle

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Abstract
A method of isolating sarcosomes, free from other components of the heart muscle, in about 50-65% yield is descr. A fractionation of heart muscle into 3 fractions[long dash]residue (myofibrillar fragments, connective tissue and nuclei), sarcosomes, and sarcoplasm-was carried out. An intermediate fraction containing both sarcosomes and microsome -like material was also obtained. The highest specific activity of respiratory enzymes (alpha-ketoglutaric oxidase system, cyto-chrome oxidase and succinic dehydrogenase) was in the sar-cosome fraction. Assuming that this is the only component of the muscle which contains these respiratory enzymes, it was calculated that the total protein was distr in the fractions as follows: residue, 49-60%; sarcosomes, 15-23%; and sarcoplasm + microsomes, 20-28%. Myokinase was found almost entirely in the sarcoplasm, which also contained a considerable proportion of the Mg-activated adenosinetriphosphatase. A number of different suspending media was employed without significantly altering the yield of sarcosomes, the activity of the alpha-ketoglutaric oxidase system or the small residual myokinase activity. From morphological and enzymic studies of the Keilin and Hartee heart-muscle prepn., it is concluded that this prepn. consists of small particles derived from the fragmentation of the sarcosomal membrane. These particles contain all except some of the early steps of the hydrogen-transferring system of the sarcosomes, but have lost many of the more soluble proteins which are found in the sarcosome. It is suggested that these proteins are in the body of the sarcosome and are liberated into the medium in a soluble form when the sarcosome membrane is broken.