Efficiency of Information Transmission by Biochemical Co-factors 



209 



the fact that the area H(B.A)-H(B.A.S) (representing antimetabolites) is 

 dependent upon the number of successful inhibitors of a co-factor which have 

 been devised. 



Over-all, the mean reduction in uncertainty in terms of actual compounds is 

 such that when confronted with fifteen compounds, assumed to be equally 



Fig. 3. Residual uncertainties associated with two co-factors. 



effective, the system can weed out ten of these, leaving the equivalent of five, 

 equally active, co-factors. Comparison of this to H(C) and H{C.A.S) is of 

 course not plausible from these figures, but clearly indicates the relative chaos 

 of the universe B, from the standpoint of the enzyme system : the assembly of 

 letter-perfect molecules of protein or nucleic acids would be impossible under 

 these circumstances. Nevertheless, these figures may have some interest as 

 the minimum limits of discrimination ability by enzyme systems. 



REFERENCES 



1. P. F. Fenton, cited by H. Quastler: The specificity of biological functions. In: Information 

 Theory in Biology, ed. by H. Quastler, 170-188, University of Illinois Press, Urbana 

 (1953). 



2. R. J. Williams, R. E. Eakin, E. Beerstecher Jr., and W. Shive: The Biochemistry of B 

 Vitamins. Reinhold Publishing Co., New York (1950). 



3. T. C. Bruice, N. Kharasch, and R. J. Winzler: A correlation of thyroxine-like activity 

 and chemical structure. Arch. Biochem. Biophys. 62, 305-317 (1956). 



DISCUSSION 



Quastler: The following interpretation of the 'residual uncertainty of co-factors' may be 

 considered : 



Given a particular apo-enzyme-substrate system, and the set B of all substances bi which are 

 or might be co-factors. Let c, be the reaction rate constant of the system in the presence of the 

 (potential) co-factor b,. Suppose that all Ci's have been determined; it seems that there are 

 two statistics of general interest: the average size of the c's, which characterizes the reactivity 

 of the system in general, and the dispersion among the c's, which characterizes its specificity. 



