520 ENZYMES DECOMPOSING SACCHARIDES. 



temperatures. Both pure invertase and dry yeast will stand heat- 

 ing, without loss of enzymatic power, to temperatures assessed by 

 A. MAYER (XIII.) at 97 0., by BAU (XII.) at 100 C. by BUCHNEII 

 (III.) at 145 C., and by SALKOWSKI (X.) at as high as 160 C. 

 According to BAU (XXVI.), yeast that has been dried at the 

 ordinary temperature or heated to 105 0. retains invertase even 

 at the end of five and three-quarter years. 



In investigating the influence of chemical reagents on inver- 

 tase, BOKEENY (IV.) followed the principle of allowing these 

 reagents to act on the yeast itself, in order to obviate any injury 

 that the invertase may suffer in preparation. He reports that 

 invertase remains unimpaired when the yeast is stored in absolute 

 alcohol for three days at ordinary temperature, or for twenty days 

 in 50-75 per cent, alcohol. The enzyme is also uninjured when 

 the yeast is kept for two days in solutions containing 0.25-0.60 

 per cent, of oxalic acid, 0.1-0.5 P er cent, of hydrofluoric acid, 

 2 per cent, of acetic acid, 2 per cent, of lactic acid or 5 per cent, of 

 formaldehyde. The enzymatic power is also not destroyed by 

 small quantities of mineral acids, alkalis, arsenites, hydrocyanic 

 acid, chloroform, phenols, toluene and thymene, both of which 

 latter were employed by EMIL FISCHER and P. LINDNER (II.) in 

 their investigations on enzymes. Similarly, BAU (XXVI.) examined 

 yeast by digestion at i2-i7 C. for twenty-nine hours, and found 

 that the invertase was destroyed by treating the yeast with i per 

 cent, and 0.5 per cent, sodium hydroxide, and o.i per cent, silver 

 nitrate, a weakening effect being produced in the case of o.i per 

 cent, mercury chloride, whereas solutions of lower concentration 

 remained inert. No injury was suffered by the invertase on 

 treatment with organic acids, including tartaiic acid of 4 percent, 

 strength. 



With regard to the influence of light on invertase, the reports 

 of workers differ. A. MAYER (XIV.) and EMMERLING (XII.) failed 

 to discover any such influence ; but according to DOWNES and 

 BLUNT (I. and II.) and also DUCLAUX (XXIX.) the enzyme is 

 sensitive towards light, especially in presence of air. Very dilute 

 acids stimulate the activity of invertase ; but the quantity used 

 must be smaller in the case of mineral acids than of organic acids, 

 For instance, according to FERNBACH (VII.), 0.0025 P er cent, of 

 sulphuric acid in the solution produces optimum activity, whereas 

 the same result requires the presence of i per cent, of acetic acid. 

 Moreover, the reports of various workers differ on this point, e.g., 

 those of KJELDAUL (I.), DUMAS (VII.), NASSE (I), LOEW (X.), 

 O'SULLIVAN and TOMPSON (I.) and FERNBACH (VI.) ; presumably 

 because they worked with invertase of divergent origin and 

 method of preparation, and containing different extraneous sub- 

 stances. According to NASSE (II.), carbon dioxide accelerates 

 hydrolysis by this enzyme, whereas carbon monoxide and oxygen 

 have the opposite effect. All alkalis and alkaline salts are said by 



