Biochemistry and Evolution 53 



Table 4. Species-specificity of insulin 



s s 



Gly Cy.Cy.Ala.Ser.Val.Cy Tyr.Cy.Asp.NH 2 



1 6 | 8 9 10 11 19 | 21 



S S 



I I 



s s 



Phe Leu.Cy.Gly Val.Cy.Gly Ala. 



1 6 7 8 18 19 20 30 



beef — Cy.Cy.AIa.Ser.Val.Cy- 



_S 



pig — Cy.Cy.Thr.Ser.Ileu.Cy- 



dieep — Cy.Cy.Ala.Gly.Val.Cy- 



horse — Cy.Cy. Thr. Gly. lieu. Cy- 



whale — Cy.Cy. Thr. Ser. lieu. Cy- 



Above, an abbreviated formula of beef insulin. 



Beloiv. points of difference between insulins of several species. 



source: Brown. Sanger, and Kitai (1955) ; Harris. Sanger, and Naughton (1956). 



the intracellular cathepsins of animals are not only qualitatively hut 

 also quantitatively homospecific with the extracellular peptidases, 

 suggesting that the extracellular peptidases of today had their evolu- 

 tionary origin in intracellular enzymes. 



Other macromolecules are not much more rewarding as things 

 stand at present. Lipids have much in common in all animals, in 

 plants, and in hacteria. Polysaccharides, apart from the remarkable 



