ENZYME COMPLEXES 



enzyme complex, are largely intramolecular in nature. We are 

 therefore dealing with electronic shifts from one part of one 

 molecule to another part rather than with electronic transfers 

 between two molecules — a vastly more rapid and efficient 

 process. Thus this representation may lead us toward an 

 explanation of those intramitochondrial events which we had 

 previously characterized by the twin attributes of efficiency and 

 control. 



Biochemical Functions of Metal Ions in Electron Transport 

 and in the Formation of Enzyme Complexes 



FORMATION OF BONDS BY COMPLEX FORMATION 



Intuitively the most obvious role of metal ions, and one 

 susceptible to experimental verification in many instances, is 

 that of linking different parts of one enzyme, or of an enzyme- 

 substrate complex (39), or of several functionally related 

 proteins. In this category we have already discussed the 

 probable function of metals in metalloflavo-proteins as sites of 

 attachment of the flavin nucleotide to the protein. This type 

 of complexing is similar to that observed by Klotz (19) in his 

 experiments on the linking of neutral dyes to protein by means 

 of metal ions. The metal has been shown to be involved in 

 forming flavoprotein-cytochrome c complexes in the case of 

 DPNH cytochrome reductase (27) and is probably so involved 

 in the reaction of all the other metalloflavoproteins with cyto- 

 chrome c as well. As a further extension of this concept it is 

 postulated that the metal is also involved in the bonding of the 

 flavoprotein and the hemoprotein moieties in the isolated in- 

 stances of aldehyde oxidase, yeast lactic dehydrogenase, and the 

 transformed DPNH oxidase. The implication of these findings 

 is then that in the mitochondrion we have similar flavin-metal- 

 hemin complexes held together at least in part by virtue of 

 chelate bonds between the various components and the metal. 

 Various cytochrome components in turn might be complexed 



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