FLAVOPROTEINS 



55 



trypsin liberating the complex into solution. Some reticulocyte response was elicited 

 by these cobalt complexes suggesting the possibility of synthesising an anti-pernicious 

 anaemia factor. The catalytic waves of cysteine in the presence of cobalt are mentioned 

 in the Polarography chapter. Coloured cobalt : histidine complexes have been 

 investigated by Michaehs (1947). 



FLAVOPROTEINS, VITAMIN Bg 

 The yellow oxidation enzyme, flavoprotein, obtained from yeast by Warburg 

 and Christian (1932), was the fore-runner of a number of flavoproteins, with the 

 properties of oxidation enzymes, that have since been described. By suitable methods 

 these flavoproteins may be split into a prosthetic group, flavin or flavin phosphoric 

 ester, and a protein carrier. The nature of this protein carrier may confer different 

 properties on the flavoprotein. The prosthetic group is dimethyl alloxazine com- 

 bined with ribose phosphoric ester and the properties of Vitamin Bg have been traced 

 to riboflavin. 



Flavoprotein effects oxidation not directly but through the intermediary of 

 coenzymes I and II as suggested in the following scheme : 



Coenzyme -f dehydrogenase -\- substrate -> Reduced coenzyme + oxidised 

 substrate. 



Reduced coenzyme -f flavoprotein -> Coenzyme -f reduced flavoprotein. 



Reduced flavoprotein + Og -> Flavoprotein. 



The oxidation-reduction reaction of flavin and the intermediate form may be 

 represented as follows (Waters) : — 



Ribityl 



CH3 

 Ri bof lavin 



Ribityl 



It has been calculated that one molecule of flavin catalyses the oxidation of 

 8,500 molecules of reduced coenzyme per minute at body temperature. 



