764 TRANSACTIONS OF SECTION I. — 



is not altogether stopped in such an organ as the mammalian kidney by pre- 

 viously heating it to 60°, by freezing, or by the prolonged action of 1 per cent. 

 NaF. H 2 2 , acting in presence of peroxidases, can likewise in some cases liberate 

 CO,, but no definite proof has as yet been obtained of such oxidation by 

 oxygenase+peroxidase, probably because oxygenases are so unstable as to be 

 destroyed very soon after a tissue is disintegrated. 



The existence of aldehyde groupings in living tissues is supported by the 

 fact that if an organ such as the kidney is poisoned with HCN, NaF, or 

 NaUSO„, its gaseous metabolism is temporarily lowered to a third the normal, 

 but on perfusion with salt solution it gradually recovers the respiratory powers 

 of unpoisoned kidneys. Now these poisons are known to be capable of forming 

 loose additive compounds with aldehydes, but other poisons, which form no 

 such compounds, permanently depress the gaseous metabolism. 



Probably there is more than one grade of oxidising power by the tissues 

 (e.g., oxygenase only, and oxygenase+peroxidase). Thus, if the vitality of the 

 tissues is depressed by the continued action of weak acids and alkalis, their 

 C0,-forming power is much more affected than their oxygen-absorbing power, 

 and the respiratory quotient falls to 0'4. The same condition is produced 

 quickly by poisoning with formaldehyde. Probably these poisons destroy the 

 tissue peroxidase more rapidly than the oxygenase. 



Doubtless other disintegrating mechanisms exist in the tissues which assist 

 the oxidation processes. It is found, for instance, that the intermediate products 

 of action of zymase on glucose can be oxidised in part to C0 2 -f H 2 by the 

 action of H„0 2 + a peroxidase, whilst pure glucose cannot. 



(iii) Oxydases. By E. Frankland Armstrong, Ph.D., D.Sc. 



Opinions are at present divided whether the oxydases arc to be regarded as 

 enzymes or as inorganic catalysts in a colloidal substrate. 



Oxydase extracts can be subjected to far more drastic methods of purifica- 

 tion than hydrolytic enzymes without destroying their activity. They in- 

 variably contain small traces of inorganic substances, generally manganese, 

 iron, and calcium salts, and careful purification fails to remove these, though 

 the amount of manganese bears no relation to the activity of the preparation. 

 1 heir behaviour can be imitated by colloidal suspensions of some inorganic 

 salts. They are far less selective in their action than the hydrolytic enzymes, 

 tyrosinase, for example, acting on d-, 1-, and dl-tyrosine apparently with equal 

 ease, and also acting on substituted tyrosine compounds so long as they contain 

 the phenolic hydroxyl group intact. 



Euler's recent observation that laccase from Medicaqci sativa can be purified 

 till it consists of a mixture of the calcium salts of polybasic hydroxy acids such 

 as citric, malic, and mesoxalic acids is of great interest. 



On the other hand, Bach takes the view that the inorganic salts are not an 

 integral part of oxydases, and do not constitute their active principle. Their 

 influence is analogous to that of ferrous sulphate on peroxides ; the salts are 

 only enabled to act because the oxydase has formed a peroxide. There is con- 

 siderable evidence of the specific nature of oxydases and of the existence of 

 different oxydases, e.g., tyrosinase, laccase. Moreover, much of the evidence 

 on the biological side is in favour of regarding the oxydases as enzymes, for 

 example, that detailed in the following note. 



(iv) The Stimulation of Oxydases and Degenerative Enzymes in the Plant. 

 By E. Erankland Armstrong, Ph.D., D.Sc. 



The leaves of the Ancuba japonica go a remarkable black colour when ex- 

 posed to the vapour of toluene, chloroform, ether, ethylacetate, alcohol, and 

 many other organic substances. A detailed investigation has shown that certain 

 inorganic salts in aqueous solution, such as cadmium iodide, mercuric chloride, 

 sodium and potassium fluoride, ammonia, but not alkalies, and some organic 

 acids, in particular benzoic and the higher homologues of acetic acid, produce 

 the blackening, all the simple inorganic salts being ineffective. 



The active substances are characterised by their possessing very little 



