^0 BIOCHEMICAL SYSTEMATICS 



work in that variations in the relative amounts of two enzymes could 

 yield differences such as reported by Kaplan, among different species 

 or within an individual. In this case, no qualitative difference in the 

 enzymes is required and the implications of the results would differ. 



Somewhat related to the work of Kaplan is that of Blagove- 

 shchenskii (1955) who has emphasized in his writings the fact that the 

 same enzymes from different organisms exhibit different activation 

 energy thresholds and particularly that more advanced organisms 

 have reduced in general the activation energy required for a partic- 

 ular enzymatic process (for example, legume catalase has lower 

 activation energy requirement than does bacterial catalase) implying 

 greater enzyme efficiency in the more advanced species. 



So far the great achievements in biochemistry have been in- 

 tegrative and unifying in their influence. The metabohc similarities 

 of all organisms, from bacteriophage (in their hmited metabolic 

 abilities), to higher plants, to man are emphasized. Examples of this 

 are so well known that it is no longer necessary to cite them. There is 

 aheady evident a turn of the tide, a focus upon minor category dif- 

 ferences in biochemistry. This thinking is expressed succinctly by 

 H. C. Crick (1958): 



Biologists should realize that before long we shall have a subject which 

 might be called "protein taxonomy"— the study of the amino acid 

 sequences of the proteins of an organism and the comparison of them 

 between species. It can be argued that these sequences are the most 

 dehcate expression possible of the phenotype of an organism and that 

 vast amounts of evolutionary information may be hidden away within 

 them. 



It is unfortunate that anyone should equate biochemical sys- 

 tematics merely with a survey of the distribution of a given chemical 

 entity. Novel situations providing challenge and reward for ingenuity 

 and perception abound in the area of biochemical systematics as in all 

 areas of biology. An example of an ingenious use of biochemical data 

 in Drosophila systematics is the work of Hubby and Throckmorton 

 (1960). It has been shown that more primitive Drosophila species 

 produce red pteridine pigments in various parts of the body while the 

 more advanced forms have the distribution of such pigments re- 

 stricted to the eyes. In the primitive forms, the red pigments are 

 present in the testes of males. The red pteridine pigments of the 

 testes are identical with the eye pigments, and the relationship sug- 

 gests an evolutionary change in pteridine metabolism in Drosophila 

 so as to restrict pteridine accumulation to the eyes where presumably 

 functional significance may be attributed to the pigment. Hubby and 



