394 ANIMAL BIOCHEMISTRY 



hydrosulfide. Another member of the group, mucoitin sulfate (page 

 70), is also comjjlexecl with proteins in the mucosa of the gastroin- 

 testinal tract. 



Most tissues of normal adult animals do not take up sulfate readily. 

 However, during healing of injuries the ion is incorporated in large 

 amounts and must be important. Furthermore, normal diets always 

 contain small amounts of many potentially poisonous compounds. 

 Some of these are detoxified by esterification with sulfate and ex- 

 creted as the sulfate esters. Animals possess enzymes catalyzing this 

 reaction, illustrated thus: 



/ /-OH + S04= + H3O+ -^^^^^^ (^ j>— OSOa- + 2H.O 



phenol phenylsulfate 



where the phenylsulfate appears in the urine with Na+. 



The sulfate reacting as shown above is first "activated" in that one 

 or more intermediate compounds is formed with sufficient available 

 free energy to drive the reaction forward. Active sulfate is believed 

 to be analogous at least in part to ATP and to be a derivative of 

 adenylic acid. 



0~ O 



I II - 



0, CHoOP — — S~0 



" ■ II II 







HO OPOgH" 



active sulfate 



The need for sulfate in animal diets is uncertain, with reports both 

 ways. Perhaps any requirement depends upon the developmental 

 stage of the animal, the presence of wounds, the quantity of cations 

 like Ca++ present that might precipitate sulfur compounds and 

 S04=, and the total sulfur intake. Nevertheless, when present, dietary 

 sulfate is utilized. For example, hens transfer radioactive sulfur from 

 sidfate ion to the albumen of their eggs. Hence, S04= may or may not 

 be essential in the diets of animals, but it is important in animal 

 metabolism and certain organic sidfates are essential animal com- 

 ponents. 



Zinc 



Microorganisms and plants require zinc. In fact certain soils are 

 so low in available Zn++ that the growth of plants is severely reduced. 



