COFACTORS OF EnZYMIC ADAPTATION 211 



The purpose of the present paper is to introduce a third 

 member into this scheme. This member will be referred to as 

 "cofactor" and the two arrows added to the scheme symbohze 

 that it is specifically involved in the autocatalysis and in the 

 heterocatalysis of a special type of the genetic material. 



NAWjsr-*- NA— *-NA — > 

 r'^^Cof actor 

 Enzyme 



At the present time the evidence concerning autocatalysis 

 is based on the study of the non-Mendelian genetic material 

 responsible for cytochrome oxidase synthesis in yeast. The 

 evidence concerning heterocatalysis is based on the study of the 

 oxygen-induced synthesis of the cytochrome system and of 

 the induced synthesis of maltozymase in yeast. Whether 

 cofactors play any role at the genie level in yeast or any role 

 in other organisms remains open for investigation. 



The discovery of cofactors is due to a systematic study of 

 conditions that are required for the induced synthesis of 

 cytochrome oxidase in yeast and to a fortuitous observation. 

 Although rather of historical interest, it may be of some use to 

 report it briefly. One of the present authors (Slonimski) has 

 been working for the past seven years on the mechanism of the 

 synthesis of cytochrome systems, and was faced quite early 

 by the fact that cells harvested at a certain phase of growth 

 cycle were unable to adapt under the usual conditions. This 

 observation is quite common to students of induced bio- 

 synthesis of enzymes. A perusal of the literature shows 

 numerous examples of decreased adaptability according to the 

 "physiological state" of the cells (Gale, 1951; Pinsky and 

 Stokes, 1952). There is no general rule and depending on the 

 organism, enzyme, and medium employed the modifications 

 occur during lag, exponential or stationary phase of growth. 

 Undoubtedly there may be numerous causes, but in general 

 they have not been properly investigated, the authors being 

 satisfied with a plausible and ad hoc explanation. This author 



