228 GEORGE H. HOGEBOOM AND WALTER C. SCHNEIDER 



As indicated in Table IV, a number of vitamins and coenzymes are con- 

 centrated in mitochondria, as well as citric acid, which was mentioned 

 above, and phospholipid. The pentose nucleic acid of mitochondria will be 

 discussed in a later section. 



c. Biochemical Properties of the Mitochondria of Tissues Other than Liver. 



There is an increasing body of evidence that the morphological simi- 

 larities of the mitochondria of different tissues" '^^ are paralleled by simi- 

 larities in biochemical properties. This observation has, in fact, been ex- 

 tended to include even the mitochondria obtained from such widely different 

 sources as unicellular organisms,^" insects (cf. footnotes 144, 145), plant 

 tissues (cf. footnote 146), and amphibia.®^ Recently, a considerable amount 

 of attention has been given to the properties of the sarcoplasmic granules 

 (or sarcosomes) isolated by centrifugation from mammalian cardiac mus- 

 g]g 147-151 jj^ general, these preparations are similar to liver mitochondria 

 both in their content of respiratory enzymes and, according to the phase 

 microscopic observations of Harmon and Feigelson,!*^ in their morphological 

 characteristics. Cleland and Slater,'^" however, report one pronounced 

 biochemical difference between heart sarcosomes and liver mitochondria: 

 the former contained only 1 % of the adenylate kinase activity of the whole 

 tissue, whereas 72% of the adenylate kinase of liver was recovered in the 

 mitochondria.^"^ Perry,^*^ on the other hand, reported a high adenylate 

 kinase activity in preparations of sarcosomes isolated from skeletal muscle 

 but, as Cleland and Slater^^" have pointed out, did not refer the activity 

 of the sarcosomes to that of the whole tissue and therefore was probably 

 not justified in arriving at cytochemical conclusions. It is readily seen from 

 the data of Table III, in fact, that adenylate kinase is such a powerful 

 enzyme that its presence in trace amounts in a single fraction could be 

 easily misinterpreted in the absence of a complete balance sheet. Cleland 

 and Slater^^" have made an additional important contribution in showing 

 that the well-known Keilin-Hartree heart muscle preparation^^^'^^^ consists 



** M. I. Watanabe and C. M. Williams, J. Gen. Physiol. 34, 675 (1951). 



" L. Levenbook, J. Histochem. and Cytochem. 1, 242 (1953). 



^^ A. Millerd, and J. Bonner, /. Histochem. and Cytochem. 1, 254 (1953). 



" G. W. E. Plant and K. A. Plant, J. Biol. Chem. 199, 141 (1952). 



« J. W. Harmon and M. Feigelson, Exptl. Cell Research 3, 509 (1952). 



^3 E. C. Slater and K. W. Cleland, Nature 170, 118 (1952). 



" K. W. Cleland and E. C. Slater, Biochem. J. 53, 547 (1953). 



" E. C. Slater and K. W. Cleland, Biochem. J. 53, 557 (1953). 



" J. W. Harmon and M. Feigelson, Exptl. Cell Research 3, 58 (1952). 



" S. V. Perry, Biochem. et Biophys. Acta 8, 499 (1952). 



6^ D. Keilin and E. F. Hartree, Proc. Roy. Soc. (London) B125, 171 (1938). 



" D. Keilin and E. F. Hartree, Biochem. J. 41, 500 (1947). 



