i2 4 SCIENCE PROGRESS 



observed increase may be due to a change in the juice by which 

 the pyrogallol oxidising enzyme becomes more active. The 

 extraordinary alterations in oxidase reactions brought about by 

 treatment with hydrogen cyanide and subsequent washing as 

 advocated by Keeble and Armstrong render it very probable 

 that such quantitative estimations are largely influenced by the 

 presence of inhibitors. The author's own work on Iris flowers 

 and other plant tissues has afforded additional evidence of the 

 widespread occurrence of these bodies. However, this does 

 not alter the fact that the functional activity of oxidase is greatly 

 increased in the affected leaves, producing, as it were, a state 

 of "fever," according to Bunzel. In this connection it may be 

 remarked that many apparent specific actions by oxidases, such 

 as the oxidation of benzidine by a tissue though it fails to oxidise 

 guaiacum, can be proved, by treatment with hydrogen cyanide, 

 to be due to inhibitors. Whether these act as genuine in- 

 hibitors, or by being themselves more readily oxidisable than 

 the added artificial chromogens, is as yet undecided. Bunzel's 

 direct measurement of oxygen absorption would appear to be 

 the most promising method of attacking this problem. 



The Bearing of Oxidase Investigations on Technology 



In addition to the interest of oxidase study for the silk and 

 sugar industries mentioned in the last section there are several 

 other more direct applications. The researches of Yoshida 1 in 

 1883 showed that an oxidase was concerned in the production 

 of the well-known black varnish obtained from the milk-like 

 sap of the lac tree, Rhus vermicifera and allied species. He 

 obtained from the sap an acid, urushic acid, which when oxidised 

 by the enzyme becomes black and forms the basis of the 

 varnish which is so much used in China and Japan. Eleven 

 years later Bertrand 2 confirmed and extended Yoshida's work, 

 giving the name laccase to the enzyme, and pointing out the 

 relationship of urushic acid to the hydroxy derivatives of the 

 benzene series. 



In the preparation of tea also an oxidase has been proved 

 by Mann 3 to play an important part. In green tea the leaf is 



1 Yoshida, Journ. C/iem. Soc. Trans. 1883, 43, 472. 

 s Bertrand, Compt. Rend. Acad. Sci. 1894, 118, 121 5. 



s Mann, H. H. Quoted from Fowler's Biological and Enzytne Chemistry 

 (Arnold, London, 191 1). 



