52 BIOCHEMICAL SYSTEMATICS 



Even more remarkable than the facts hsted above are the 

 imphcations of recent work by Zuckerkandl et al. (1960) who have 

 utihzed trypsin lysis of hemoglobins of various animals and have then 

 examined the patterns of the derived peptide mixture by means of 

 combined electrophoresis and paper chromatography. Although it is 

 admitted that comparison of individual spots is limited by the 

 methods, the authors suggest that when two complex peptide pat- 

 terns are generally similar the probability is high that most of the 

 spots represent identical or highly similar sequences. Among several 

 primates studied the basic patterns were very similar; other mammals 

 showed less similarity to the primates than did primates to each 

 other; three fish patterns (bony fish, lungfish, and shark) showed few 

 similarities, and a cyclostome and Echiurid "worm" showed none. 

 The three fish patterns differed among themselves more than did the 

 mammals observed. Apparently most of the hemoglobin molecule has 

 been subject to the effects of gene mutations which have been retained 

 in the course of vertebrate evolution,^ and probably mutations affect- 

 ing the same peptide region have occurred repeatedly. The hetero- 

 geneity of these hemoglobins is remarkable in itself, but even beyond 

 this, it suggests that this type of comparative biochemical study may 

 be expected to make a major contribution in the not too distant future. 

 Enzyme heterogeneity is now well established, and a major conference 

 has already been devoted to the question of multiple molecular forms 

 of enzymes (Wroblewski, 1961). Introductory remarks at this con- 

 ference, held by the New York Academy of Sciences, by Gregory (1961) 

 reflect the current lively interest and realistic possibilities of studies 

 of the comparative biochemistry of enzymes: 



It is apparent that enzyme heterogeneity is a common phenomenon. 

 More than 30 enzymes have been shown to exist in multiple forms 

 within individual organisms. They have been observed in both plants 

 and animals, in unicellular microorganisms as well as multicellular 

 species. They have been distinguished on the basis of a variety of 

 characteristics including electrophoretic and chromatographic be- 

 havior, serological specificity, differential solubility, and differential 

 response with coenzyme analogues. . . . The importance of the study 

 of multiple forms of enzymes stems in part from their frequent but by 

 no means universal occurrence. Their study promises to expand our 

 knowledge in a variety of fields ranging from embryology and the 

 study of evolution to physiology and pathology.* 



3 For an interesting discussion of the evolution of hemoglobin and myoglobin, see 

 V. M. Ingram, "Gene evolution and the haemoglobins." Nature, 189: 704-708 (1961). 



