416 IX. HEMATIN ENZYMES, II 



In general, the catalase content of human blood is approximately Wiit not 

 completely parallel to its red cell content iolJ4<S.i). Further references are 

 given in the papers quoted. In general, anemia is frequently associated 

 with reduced blood catalase activity but on recovery catalase rises more 

 rapidly than does hemoglobin, young red cells being perhaps particularly rich 

 in catalase. During the first months of life the catalase activity is relatively 

 smaller than later. 



Needham {2017, p. 004) states: "Contrary to a persistent belief it is not 

 possible to show any relation between catalase activity and respiratory 

 intensity." If, however, the activity of catalase is compared with the amount 

 of cytochrome system which can be shown to be present, the experiments of 

 Williams [SOSIi) on grasshopper egg development appear to make a rather 

 good case for correlation, except that in the first days of prediapausal devel- 

 opment catalase appears more slowly than the cytochrome system. In the 

 development of the embryo the ratio of catalase to unit weight increases and 

 the increase of catalase is inversely proportional to anaerobic glycolysis 

 (cf. ^Oi7, p. 604). 



2.7.2. Protection against Hydrogen Peroxide. Until quite 

 recently it has been generally assumed that catalase serves the biolog- 

 ical purpose of protecting the cell from the deleterious effects of 

 hydrogen peroxide. 



It has been shown in Chapter VIII that the autoxidation of ferrous 

 cytochrome oxidase produces no hydrogen peroxide, but it is well 

 known that several enzyme systems, such as amino acid oxidase, 

 amine oxidase, polyphenol oxidase, glucose oxidase, xanthine and 

 aldehyde oxidase, and uricase (aerobic dehydrogenases), produce 

 hydrogen peroxide, and that the latter may be also formed by the 

 autoxidation of flavoproteins, sulfhydryl compounds, and ascorbic 

 acid. Dixon {595) showed that catalase, in fact, protects xanthine 

 oxidase from destruction by the hydrogen peroxide which it forms. 

 L. Stern {2662) found a certain proportionality between the concen- 

 tration of the aerobic dehydrogenases in organisms and their catalase 

 content. Hydrogen peroxide has not been observed, however, in 

 strongly respiring cells of aerobic organisms, even if catalase was 

 inhibited by hydroxylamine. Keilin believes that the small oxygen 

 affinities of the aerobic dehydrogenase systems make it questionable 

 whether these systems actually function in the cells of higher organ- 

 isms, in which the oxygen pressure is low. 



In this connection it, is of some interest that Ascaris contains but 

 little catalase and cytochrome c {1655); this worm lives under nearly 

 anaerobic conditions and is damaged by higher oxygen pressure. 



In plants, hydrogen peroxide has been shown to be formed, although 



