Asu, "Which Compound in certain plant-juices can liberate iodine etc. 209 



well, but not a trace of the iodine reaction. I applied for one 

 volume of this Solution x f% — 1 / 2 volume of a 2°/ starch paste to 

 which l°/o potassium iodid and 0,5°/ o acetic acid was added. 

 These mixtures yielded even after twentyfour honrs standing in 

 darkness, no trace of any blue reaction, while the guaiacum 

 blue reaction even in absence of hydrogen peroxid was still 

 obtained with great intensity 1 ). Bach and Chodat recommend 

 to add some manganosulfate in those cases in which the iodine 

 reation with plant juices fails. But in the above mentioned 

 cases with the juices of potato pea and radish, this sulfate did 

 not change the result. 



In order to decide whether the oxidizing enzyms are really 

 organic peroxids, I have made the following experiments relating^ 

 to the special oxidizing enzym, which produces a red color which 

 a 1 % guaiacol Solution in presence of a weak acid reaction. The 

 juice of the leaves of radish contains besides oxidase and 

 common peroxidase, also a peculiar oxidizing enzyni which 

 produces the red reaction just mentioned 2 ). This juice was 

 mixed with Yio of its volume of a hydrogen peroxid of about 

 2°/o and of a faint acid reaction. After five minutes standing 

 about four times the bulk of absolute alcohol was added and 

 the precipitate washed very well with alcohol. This precipitate 

 was then dissolved in some water and tested with rmaiacol, but 

 no reaction wathever was taking place. If Kastle and Loewen- 

 hart's view 3 ), that also peroxidases were nothing but organic 

 peroxids, was correct, then the supposed organic peroxid must 

 be fornied almost instantaneously when hydrogen peroxid comes 

 in contact with the proper organic material in the juice. This 

 supposed organic peroxid would consequently be also present in 

 the alcoholic precipitate containing all the oxidizing enzyms, 

 hence the aqueous Solution of this precipitate ought to give now 

 the red guaiacol reaction without the further aid of hydrogen. 

 peroxid, but the fact was: no reaction in absence, but an 

 intense reaction in presence of hydrogen peroxid. What is true 

 for this kind of peroxidase (ß - guaiacolase) is very probably 

 also true for the common peroxidase characterized by the blue 

 coloration with guaiacum tincture an hydrogen peroxid 4 ), but 



x ) In one case I had applied intentionally a potassium iodid Solution 

 not freshly prepared, but one which. had been exposed in presence of air 

 for a few days to sunlight. In this case, a blue reaction was gradually 

 observed, evidently due to slight traces of free iodine formedinthis Solution. 



2 ) Since Bourquelot observed in the fungus Bussula an oxidizing 

 euzym which produces a red color with guaiacol even in absence of hydrogen 

 peroxid, I propose to distinguish this peculiar enzym as a- guaiacolase, from. 

 the abovementioned enzym which I call ß - guaiacolase. About this reaction 

 compare also my article, on oxidizing enzyms in the vegetable body. (Buk 

 CoUege of Agric. Tokyo. Vol. V. No. 2. p. 207—235.) 



3) Americ. ehem. Journ. XXVI. 1901. No. 6. Dez. 



4 ) On heating the Solution of the enzym precipitate above-mentioned 

 for 5 minutes to 75° C. the oxidase and the common peroxidase are killed, 

 while the guaiacol - hydrogen peroxid - reaction was still obteined, although 

 weaker than before the heating. 



Beihefte Bot. Centralbl. Bd. XV. 1903. 14 



