CATALYSIS: THE GUIDE OF LIFE 127 



the oily or lipid layer. Since chloroform, urethane, urea, heat 

 and detergents (Duponol, Areosol) all produce the same final 

 effect (active tyrosinase), Bodine states: 



"The enzyme, tyrosinase, is protein in nature and as such shows 

 all the characteristic properties of this chemical group of com- 

 pounds. It, therefore, would seem logical to expect that activation 

 may possibly be related to or dependent upon some physio- 

 chemical properties of this protein molecule and that the various 

 activators employed bring about just such changes. Without add- 

 ing unnecessary details in the way of experimental data, it may 

 be stated that the activation of the melanin-producing enzyme in 

 the present studies is thought to be brought about by the selective 

 adsorption and orientation of the pro-enzyme molecules by the 

 activating agents." Activation ceases to increase when the acti- 

 vator surface is occupied, either by pro-enzyme, or by another 

 adsorbed protein. 



The black spots on a Dalmatian dog appear where the local cells 

 enable the melanin-producing process to occur, the remaining hairs 

 being white. L. Earle Arnow 71 found that in the presence of oxygen, 

 tyrosine may be converted by ultraviolet light into dopa, which is 

 then changed into melanin by an oxidase. Sun-tan appears to be so 

 caused in some persons. A curious case of inhibition of skin pigment 

 formation appeared in a large tannery, where a considerable number of 

 workers (about 50 per cent, many of them Negroes) developed white 

 patches on their skins. Investigation showed that the rubber in some 

 new gloves used to protect the workers' hands from an acid solution, 

 had contained the monobenzyl ether of hydroquinone as an antioxi- 

 dant, and that this substance also inhibits melanin formation; so that 

 when the melanin originally present in the skin is absorbed or other- 

 wised removed, the skin turns white (leukoderma). When the cause 

 was removed the skin slowly returned to its normal shade, indicating 

 that the pigment-forming mechanism was merely inhibited by the anti- 

 oxidant, not destroyed. Normal skin color thus seems to represent 

 a balance between pigment formation and removal. 



E. L. Tatum and G. W. Beadle state: 72 "The development of eye 

 color in Drosophila is known to be controlled by specific diffusible 

 substances designated as v + and cn + hormones." By growing certain 

 bacteria on an agar medium containing dead yeast, sugar, and /-trypto- 

 phane, "this bacterially produced v + hormone has now been obtained 

 in a pure crystalline state," with "an activity of approximately 20,000,- 

 000 v units per gram when a solution is injected into vermilion brown 

 test larvae." 



