METABOLIC PROCESS PATTERNS 



electron system. The available potential between oxygen and a pair 

 of average substrate hydrogens is 1.2 v., a potential span which may 

 accommodate theoretically 1.2 divided by 0.25, or 4+ energy-rich 

 bonds. This calculation fixes the upper limit of yield and shows the 

 experimental values to be well within this limit. 



In the particular scheme of Figure 2, a generation of the three 

 phosphate bonds established by experiment is rationalized by merely 

 cutting out, from the potential gradient, three 0.25-v. portions in 

 succession. Such a mapping leads to the conclusion — unambiguously, 

 it would appear — that at potential levels of around +0.1, +0.5, and 

 +0.9 v., with reference to the hydrogen electrode of pH 7, the pair 

 of hydrogen electrons is intercepted three times in succession by 

 chemical devices which transform catalytically 0.25-v. portions into 

 energy-rich phosphate bonds. This breaks the process of hydrogen 

 transfer up into three smaller units; and here we probably meet the 

 smallest units of the catalytic system designed for respiratory trans- 

 formation of energy. The three, or perhaps four, transformers which 

 are built into the pathway of the hydrogen electrons should be con- 

 sidered as the actual power generators of the living organism. It is 

 very significant that these transformer systems appear largely inde- 

 pendent of the particular hydrogen donor. Such operation of sub- 

 strate-independent catalysts for transformation may explain how 

 phosphate bonds are generated in a constantly increasing variety of 

 oxidations, such as sulfur oxidation in Thiobacillus (16), the oxyhy- 

 drogen reaction (3), and fatty acid oxidation (13). To summarize, 

 we may say that generation of phosphate bonds, regardless of the type 

 of hydrogen donor, may be represented by the following equation: 



XH2) 



or > + 3 HO-POa" + 3 ad-H + O2/2 > 



X-HaO) 



or > + 3 ad ~ PO3— + 4 H2O; 



xo) 



average AFo, (3 X 12) - 57 = -21 kcal. (2) 



Equation (2) shows that a participation of phosphate and adenylic 

 acid frequently is a reflection of general hydrogen transfer catalysis 

 rather than a particular case of dehydrogenation. 



