Oxidation Systems of Organisms 



565 



the enzyme paraperoxidase (peroxidase I). By differential adsorption on alumina 

 gel Kondo & Morita [7] isolated two peroxidases (a and b) from the sweet potato, 

 Jermyn & Thomas [8], by electrophoresis on paper, separated the peroxidase of 

 horse radish into first four and later five components. The ratios in which they 

 occurred varied with the time of year. In the spring, for example, only three of 

 the five components were found. One of these is constantly present in the juice 

 of the horse radish and corresponds with Theorell's crystalline peroxidase. The 

 other two both carried a negative charge at pH5 but differed in their substrates. 

 For example, one of them is characterized by a positive peroxidase action on 

 benzidine and none on guaiacol, while the other component, on the contrary, 

 mainly oxidized guaiacol. 



Nelson & Dawson [9] separated the polyphenol oxidase of the mushroom, 

 Psalliota campestris, into two components, differing from one another in their 

 abilities to oxidize catechol and cresol. These differences were associated with 

 particular features of the protein molecules of each of the enzymes. In our 



Oct. Nov. Dec. Jan. | Feb. ^_ 



Fig. I . The part played by different groups of oxidases in the respiration of the 

 peel of a lemon at different periods in the life of the fruit (% of total respiration). 



laboratory it has been shown that, in the tissues of citruses, an aldehyde oxidase, 

 an amino acid oxidase and a glucose oxidase are all present. 



Evidence has recently been obtained indicating that some cellular hydrolases 

 are also made up of many components. Thus, GilHgan & Reece [10] have shown 

 that the 'cellulase' of a number of bacteria may be separated chromatographically 

 into several enzymes which may be distinguished by their abilities to break down 

 carboxymethylcellulose, native and swollen cotton fibres etc. 



A very important feature of the catalytic apparatus of the plant cells is their 

 inconstancy, the variability of the ratios of the different components of the 

 complex to one another. 



This concerns what is known as the shift of the enzymic systems during the 

 ontogenesis of the plant. It was described by Sisakyan & Rubin [11] in the leaves 

 of apple trees, and by MikhHn & Kolesnikov [12] in the shoots of barley and has 

 since been confirmed by the work of many other investigators on the most varied 

 material. 



I will give two of the many available examples. According to our evidence, in 

 citrus fruits, during the course of their development, one may observe a regular 

 replacement of metal-containing oxidases by flavoprotein enzymes. This re- 



