124 



UNITY AND DIVERSITY IN BIOCHEMISTRY 

 OH OH 



OH 



►/ 



v 



(O) 



Enzyme 



W/ 



V 



OH 



O 



^ (O) 



Enzyme 



o 



V 



Similarly, phenolase oxidizes o- and p- polyphenols. 

 In the course of these reactions, cupric copper of the phenolase is reduced 

 to cuprous copper which is again oxidized by oxygen. 



OH O 



2Cu^-+ + 



(j 



OH 



2Cu^ 



V 



o 



2H+ 



V 



2 Cu+ + 2 H+ -\- 1/2 O,-^ 2 Cu++ + H.O 



There are many uses made of the properties of the cupriprotein phenolase, 

 both in plants and in animals : respiration, biosynthesis, scelerotization of 

 cuticles, pigmentation, etc. 



2. Haemocyanins 



These cuproproteins are oxygen carriers found in certain animals 

 belonging to the mollusc and arthropod families. They are blue in the 

 oxygenated state and colourless in the reduced state. The spectrum of 

 haemocyanin is very similar to that of any copper-protein in which cupric 

 copper is bound to an -SH group. 



The absorption spectra of oxyhaemocyanin in the visible and ultraviolet 

 regions (Figs. 23 and 24) can be superimposed on the spectra of copper- 

 serum albumin in which the copper is attached to a sulphhydryl group. 



{b) Proteins Binding Iron 

 Examples of this widely distributed type of compound are the haemery- 

 thrins, ferritin and transferrin. 



1. Haemerythrins 



These are large molecules of protein and iron in which the iron, according 

 to Klotz and Klotz, appears to be partly ferrous and partly ferric. The 

 haemerythrins which can be oxygenated like the haemoglobins, chloro- 

 cruorins and the haemocyanins, like these substances, function as oxygen 



