FIELD T-2 

 Columns 58, 59, 60, and 61 



altered is implicit in the name of the enzyme. From the standpoint of retrieval of information, this may 

 represent a disadvantage, however, since in programming retrieval of information on any given biological 

 compound (or biological compound type), if the plan included a search for the compound treated as a 

 secondary compound (Field D), Field T-2 must be searched for enzymes known to affect that particular 

 biological compound. Thus, it is suggested that it might be more advantageous, in another coding 

 program, always to code Field D with the compound altered in spite of the fact that the coding of Field 

 T-2 adequately implies the identity of the altered compound. 



The coding of Field T-l, when Field T-2 is coded with an enzyme, is according to the following 

 pattern: 



When the test compound inhibits the enzyme, use Symbol 2 or 3. 

 When the test compound stimulates (potentiates) the enzyme, use Symbol 1. 

 When the test compound is a coenzyme to the enzyme, use Symbol 7. 

 When the test compound affects the action of a secondary compound on the enzyme, use 

 Symbol 8, 9, A, or C. 



Information about the effect of an enzyme on the test compound is not coded by the CBCC, when 

 the effect is expressed by naming the enzyme and when the enzyme is coded in Field T-2. Effects on 

 test compounds are coded only by symbols of series FE-- when the specific alteration is named. This 

 is discussed in Division 26. 



Information about the effect of the test compound on the enzyme (rather than on the action of 

 the enzyme), such as the amount, synthesis, or destruction of the enzyme, is not coded. 



When the test compound has an effect on metabolism through its effect on any enzyme, the 

 enzyme should be coded in Field T-2 rather than to translate the enzyme action into one of the metabo- 

 lism symbols of the Field T-2 F symbol series. 



When the effect of a test compound on an enzyme is coded, the organism source of the enzyme 

 should be coded in Field E, the organ or tissue source should be coded in Fields H-l and/or I, and 

 Field G-l should indicate the state of the organ or tissue source (e. g. , extract or slice of the tissue, 

 Symbol V or X of Field G- 1 ). 



Appended to the Taxonomy Code of Field E are three special items, to be used only for indicating 

 general sources of enzymes when the specific organism source is unknown or is not specified by the 

 author. These are Symbols Z, Zl, and Z2. 



The section of Field T-2 which lists specific enzymes with their code symbols is designated as 

 the Enzyme Code. These Field T-2 code symbols do not represent CBCC chemical serial numbers nor 

 do they reveal the structure of the enzyme; they are special symbols conforming to the pattern of Field 

 T-2, having four units. The first unit (7) identifies the item as being an enzyme, the second (Column 59) 

 indicates the general type of enzyme, the third (Column 60) specifies either a sub-type or a specific 

 enzyme of the type indicated by the second unit, and the fourth and final unit (Column 61) indicates a 

 specific enzyme of a sub-type specified by the third unit. Since enzymes are named for the substrate 

 whose alteration they catalyze, the symbols reflect this information by their structures. 



It was intended that the enzyme list be revised at frequent intervals or continually, to keep it 

 up-to-date. Circumstances have not permitted this. The last revision was in 1953; the following is 

 quoted from the introduction prepared by Dr. I. D. Welt for that edition: 



"The classification of enzymes is difficult because of the relative non- specificity of some 

 of these substances and also because of the lack of agreement among enzymologists. It is 

 possible in some codes at least to assign a given enzyme to more than one category, and a 

 classified listing such as the one presented must be regarded as tentative and subject to revision 

 when more becomes known about the intimate details of the reactions which are catalyzed. In 

 the indexing of enzymes, certain broad groups have been selected as a suitable arbitrary pattern 

 for classification. 



148 



