558 ENDOTRYPTASE AND PHILOTHION. 



may be explained by the action of endotryptase, for which the 

 application of antiseptics affords no remedy. It will be a difficult 

 matter to counteract this influence of endotryptase, though, 

 certainly, the formation of endotryptase might be hindered, and 

 the yeast consequently preserved, by improving the machinery 

 so as to shorten the time occupied in washing. Again, it is 

 not always right to assume that the rapid decomposition of the 

 finished cakes of pressed yeast in the warm weather is due to 

 the agency of bacteria, these latter very often only coming into 

 action secondarily, after the way has been prepared for them by 

 the death of the yeast cells and the action of the endotryptase. 



336. Philothion. 



J. DE REY-PAILHADE (I.), in 1888, was the first to observe 

 the faculty of an alcoholic extract of yeast to convert elementary 

 sulphur into sulphuretted hydrogen. For this reason he named 

 the active principle (enzyme) of the extract "philothion," which 

 name he afterwards (VIII.) changed to " hydrogenase." An 

 extract of this kind is easily prepared by treating yeast at ordinary 

 temperature either with pure methylalcohol or with 86 per cent, 

 ethylalcohol, the resulting yellow liquid being forced through a 

 biscuit-ware filter in order to free it from cells. The extract 

 becomes inactive on being kept at 70 0. for two hours. Accord- 

 ing to the same author (III.), the reducing power of this yeast 

 enzyme is not restricted to sulphur, oxygen also coming within its 

 .sphere of activity, the yeast extract losing its powers when exposed 

 to the air for a few days. The sensitivity of philothion, however, 

 towards oxygen is not great, since it has been found by A. 

 WROBLEWSKI (I.) in an active condition in expressed yeast juice 

 prepared without exclusion of air (see pp. 462, 463, vol. ii.). The 

 negative results of G. COSSETTINI'S (I.) attempt to confirm the 

 reports of Rey-Pailhade seem attributable to the usual incapacity 

 of enzymes to pass through the Chamberland filter (see p. 98, vol. i.) 

 in certain circumstances. 



Up to the present, philothion has not been isolated and 

 prepared in a pure state ; and it is known and characterised solely 

 from its reactions. It belongs to the group of the reductases, 

 another member of which has been mentioned on p. 374, vol. ii., 

 namely jacquemase, and from the whole of which it differs by its 

 characteristic action on free sulphur. Pozzi-EscoTT (II.) states 

 that it is also able to convert phosphorus and selenium into their 

 hydrogen compounds though it has no such action on tellurium or 

 arsenic. According to REY-PATLHADE (IX.) free nitrous acid is 

 destroyed by philothion very rapidly at 40 C., but more slowly 

 at ordinary temperature. This power is crippled by dilute hydro- 

 chloric or sulphuric acid. In addition to being present in the cells 

 of species of Saccharomyces and Torula (see pp. 397, 398, vol. ii.), 



