RESPIRATION AND OXIDATIVE PHOSPHORYLATION 



111 



Table II. Relative proportions of respiratory enzymes, concentration and 

 turnover number of cytochrome a in dog and Spisula spermatozoa 



" Amytal present in reference cuvette. 



spermatozoa. This applies to both the relative proportions and ab- 

 solute concentrations of the cytochromes. The high proportion of 

 cytochromes a and a s , compared with other components of the re- 

 spiratory chain, is unusual for mammalian cells and resembles some- 

 what the situation in muscle tissues of lower vertebrates such as the 

 toad (Chance and Hess, 1959; Ramirez, 1959). The presence of cyto- 

 chromes a and a z in equal amounts was further confirmed by spectra 

 recorded after carbon monoxide treatment. To estimate the amount 

 of cytochrome c 1 , bull spermatozoa were exposed to distilled water 

 for one hour at 5°C, which resulted in a loss of cytochrome c without 

 decreases in other pigments (Estabrook, 1958). Comparison of spectra 

 obtained with an extracted sample and one treated only with saline 

 showed that there is roughly a 1 to 1 ratio between cytochromes c 

 and c r 



In dog and bull sperm the cytochromes appear to exist approxi- 

 mately in the ratio, 3a 3 :Sa:lc: \c x :\b, and in Spisula sperm, la. d :la: 

 \c: \(b) (Gonse, 1959a,b,c). In the latter case, it is impossible to ascer- 

 tain whether the (b) term represents one unit of 6(557) for one of 

 6(560); if such be the case, one of the b components could be con- 

 sidered as playing the part of cytochrome c 1 of bull or dog sperma- 

 tozoa. 



While the proportions between various cytochromes are different 

 in these two kinds of spermatozoa, their respiratory activity is of the 

 same order of magnitude as is shown by a comparison of concentra- 

 tion and turnover number for cytochrome a, designated TN a (Table 

 II). 



The TN a of Spisula spermatozoa is 1.3 sec -1 , which corresponds to a 



