The Nature and Diversity of Catalytic Proteins 91 



Conclusions 



The audience is perhaps too well aware at this stage of the validity 

 of a comment made at the beginning of this address, namely, that the 

 topic under discussion is broad. Many other facets than these cited 

 herein could be given for your consideration. In any event it is clear 

 to the lecturer, and I hope to the audience, that the basis for the 

 nature and diversity of catalytic proteins is at best only partly 

 understood. It must be emphasized that the occurrence, properties, 

 and mechanism of enzymes from widely different cells are more 

 striking than the differences. In some instances, however, as with 

 yeast and muscle aldolase, rather wide differences in mechanism do 

 appear possible. With regard to enzyme mechanisms, continued 

 search may reveal more basic and simplifying generalities underlying 

 the behavior of enzymes. Some common mechanistic patterns already 

 recognized have been discussed briefly, and possibilities of further 

 generalizations have been mentioned. The problems sketchily outlined' 

 herein call for zealous application of man's ingenuity. It is from the 

 probing at and documenting of the diversities of enzymes and their 

 action that important generalizations about living processes will 

 emerge. 



ttvfvi'VIH'PS 



1. C. L. Markert and F. Mcdler. Multiple forms of enzymes: tissue ontogenetic and 

 species specific patterns. Proc. Nat. Acad. Sci. U.S.. 45:753-765 (1959). 



2. J. S. Nisselbaum and 0. Bodansky, Reactions of human tissue lactic dehydro- 

 genases with antisera to human heart and liver lactic dehydrogenases. J. Biol. 

 Chem., 236:401-404 (1961). 



3. N. 0. Kaplan. M. M. Ciotti, M. Hamolsky. and R. E. Bieber, Molecular hetero- 

 geneity and evolution of enzymes, Science, 131:392-397 'I960). 



4. P. D. Boyer. Mechanism of enzyme action. Ann. Rev. Biochem.. 29:15-44 ( 1960). 



5. F. Sanger and D. C. Shaw. Amino-acid sequence about the reactive serine of a 

 proteolytic enzyme from Bacillus subtilis, Nature (London). 187:872-873 

 (1960). 



6. E. F. Jansen. M. D. F. Nutting, and A. K. Balls, Mode of inhibition of chymo- 

 trypsin by diisopropyl fluorophosphate. I. Introduction of phosphorus. J. Biol. 

 Chem.. 179:201-204 (1949). 



7. R. L. Hill and E. L. Smith. Hydrolysis of mercuripapain by leucine amino- 

 peptidase without loss of enzymic activity, J. Biol. Chem., 231:117-134 (1958). 



8. O. Nylander and B. Malm Strom, The degradation of yeast enolase with leucine 

 aminopeptidase and carboxypeptidase without change in enzymic activity; N- 

 and C-terminal residues of the enzyme, Biochim. et Biophys. Acta. 34:196-202 

 (1959). 



9. F. M. Richards and P. J. Vithayathil, The preparation of subtilisin-modified 



