264 SCIENCE PROGRESS 



xanthin into uric acid. Another oxidase which is present in 

 watery extracts of dog's liver has the power of oxidising /3- 

 oxybutyric acid to aceto-acetic acid, 1 and this aceto-acetic acid is 

 in turn split up still further by some other enzyme. Still another 

 soluble oxidase is able to oxidise ethyl alcohol to acetaldehyde 

 and acetic acid. 2 However, it is extremely feeble in its action, 

 ioo gm. of fresh horse liver oxidising only o' i gm. of ethyl alcohol 

 in an hour at 40 , whilst it attacks other alcohols still more 

 slowly. The so-called aldehydase described by Schmiedeburg 

 and others is really not a true oxidase at all, but merely a 

 hydrolytic enzyme which converts salicylaldehyde into equal 

 quantities of saligenin and salicylic acid. 3 



Many invertebrate animals, such as lepidoptera, worms, and 

 certain Cephalopods, contain a specific enzyme which oxidises 

 tyrosin to a brown melanin. This oxidase is also present in the 

 skin of the frog, whilst an enzyme can be extracted from the 

 skin of rats and guinea-pigs which will oxidise tyrosin to various 

 coloured pigments if a trace of iron sulphate is added as 

 activator. 4 V. Fiirth and Schneider 5 think that tyrosinase is 

 responsible for the formation of melanotic pigments in all 

 animals, but there is at present no definite proof of this 

 hypothesis, except that Gessard 6 found tyrosinase in a melanotic 

 tumour. In addition to tyrosinase, some animal tissues contain 

 phenolases which oxidise guiaconic acid to guiacum blue, 

 pyrogallol to purpurogallin, and effect other phenol oxidations, 

 but they are not nearly so powerful or so widely distributed as 

 in vegetable tissues. They are present in the haemolymph and 

 blood of various invertebrates, and in some of the tissues, whilst 

 in vertebrates they seem to be confined to leucocytes and a few 

 secretions as the saliva. 7 



It will be noted that the oxidations effected by the oxidising 

 enzymes of the tissues are for the most part not nearly so 

 powerful as those induced by H 2 0_, + FeSO*. In one or two 

 instances they led to the production of C0 2 , but food stuffs such 

 as carbohydrates and fats are practically untouched by oxidising 



1 Wakeman and Dakin, Journ. Biol. Chem. 6, p. 373, 1909. 



2 Battelli and Stern, Biochem. Zeit. 28, p. 145, 19 10. 



3 Battelli and Stern, ibid. 29, p. 130, 1910. 



4 Miss Durham, Proc. Roy. Soc. 74, p 390, 1904. 



8 V. Fiirth and Schneider, Hofvieister's Beitr. 1, p. 229, 1901. 



6 Gessard, C. R., 138, p. 1086, 1903. 



7 Cf. Battelli and Stern, Ergeb. d. Physiol. 12, p. 157, 1912. 





