EFFICIENCY OF INFORMATION TRANSMISSION 

 BY BIOCHEMICAL CO-FACTORS* 



Peter D. Klein 



Division of Biological and Medical Research, Argonne National Laboratory, 



Lemont, Illinois 



Abstract — Amodelfor the transmission of information by biochemical co-factors is described. 

 Two points of information transfer are apparent : formation of the holo-enzyme and formation 

 of the holo-enzyme-substrate complex. The reduction in uncertainty taking place at these 

 points is related to the sets of compounds existing before and after these points, and the values 

 for artificial situations calculated. 



It is concluded that the artificial situation is an estimate of the minimum selection capabili- 

 ties of the enzyme system. 



Co-factors are compounds of molecular weight 100 to 2000 which participate 

 in a host of biochemical reactions. They are not metabolised per se, but serve 

 as catalysts. The moiety with which co-factors cooperate may in this instance 

 be limited to proteins. Co-factors for a particular protein may be either 

 exogenous (vitamins) or endogenous (hormones). 



The flow diagram (Fig. 1) represents the fate of a co-factor in the organism. 

 A particular apo-enzyme can operate on a substrate or class of substrates if 

 provided with the suitable co-factor. In this case the co-factor is assumed to 

 be a vitamin. Therefore, preliminary to its appearance in the cell, the com- 

 pound must of necessity be ingested, absorbed and transported into the cell. 

 Inside the cell, the compound may or may not be excreted again. Each time 

 that it exists in a 'free' form, it has a finite possibility of leaving the site of 

 action, including transformations which lead to the degradation of the molecule 

 so that it cannot function. This possibility is represented by Probability Point 1 . 

 This and subsequent probability points have the following characteristics: 

 A molecule 'passing' through this point may undergo two or more transitions; 

 each state resulting from these transitions has a certain probability but there is 

 no control over the state into which the molecule passes. 



Next, it may be imagined that a collision between the compound and the 

 apo-enzyme for which it may be destined takes place, leading to the formation 

 of a complex. The formation of this complex, however, depends upon mutual 

 exchange of information between the apo-enzyme and its co-enzyme and is 

 indicated by Decision Point 1 . For example, if the co-enzyme for cocarboxylase 

 collides with the apo-enzyme for riboflavin, no information exchange takes 

 place and there is no complex formation. If, however, sufficient information 

 is exchanged, there results the formation of the holo-enzyme, or in the case of 

 the competitive inhibitor, a pseudo-holo-enzyme. Both forms of holo-enzyme 

 have, of course, a dissociation constant, indicated by Probabihty Point 2. 



* This work was performed under the auspices of the U.S. Atomic Energy Commission. 



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