Nutrition Investigations. 275 



(131) find in the case of dwarf beans that when the food is wholly dex- 

 trose administered to the leaves, pentosans increase greatly, especially 

 in the light, and that when the functioning of chlorophyll is prevented 

 for long periods the amount of pentosans decreases. They conclude 

 that the simple sugars exert a preponderating influence in pentosan 

 formation, and that these serve as a reserve material when the plant 

 has exhausted its more readily available food materials. 



PENTOSANASES IN THE VEGETABLE KINGDOM. 



Our knowledge of enzymes inverting pentosans is meager, and rather 

 indefinite. The action of such forms as Hymenomycetes upon wood 

 seems to be of chemical nature. At any rate it is evident (107-146) 

 that they are able to utilize xylan. Bourquelot and Herissey (95) have 

 isolated an enzyme from malt diastase which produces reducing sugar 

 from pectins, and call it pectinase. This is not to be confused with 

 the so-called pectase which causes the coagulation of pectin bodies. 

 Bigelow, Gore and Howard (92) also find that the enzymes of Asper- 

 gillus partially hydrolyze the pectin of gentian root. According to 

 Harrison {1\^) , Bacillus o^erace^ produces a cytase capable of dissolv- 

 ing the cell walls of potatoes, turnips, cauliflower and allied plants, 

 which acts particularly on the middle lameUa, the supposed seat of 

 pectin. 1 The latter is not an inverting enzyme. In Persian Berries 

 {Rhamnus) (162), in Penicilliwn glaucum, and Botrytis cinerea (90), 

 an enzyme (rhamnase) has been found which splits off rhamnose from 

 some of its glucosides {rhamnetin and rhamnazin). An early observa- 

 tion of the presence of rhamnase in the rutin of garden rue was made 

 by Borntrager (94). That some of the so-called cytases described 

 under cellulose'- may act on pentosans seems possible, but there is no 

 direct evidence that such is the case. On the contrary, Cross and 

 Bevan (105) believe that pentosans once formed in the plant, remain 

 thenceforth unaltered. 



Tollens and Glaubitz (159) assert that the pentosans do not undergo 

 lactic or butyric acid fermentation, and are otherwise unaffected by 

 yeast, as has also been shown by Lintner and Diill (125). The pento- 

 sans are very resistant toward the action of bacteria. Slowtzoff (154) 

 found that a small amount of pure xylan in a putrefying mixture. 



'Cf. Czapek, Biochemie der Pflanzen. 



-a. Biedermann and Moritz (34), Brown (35), Brown and Morris (36), Berg- 

 mann (32), Gruss (184), Newcombe (64). 



