The isoelectric fractionation of hen's-egg ovotransferrin

1. ATP sulphurylase was assayed in various organs from vitamin A-deficient and pair-fed control rats at different stages of deficiency. Activity decreased slightly in the liver and markedly in the adrenal gland. Striking differences in liver activity were observed between pair-fed control and ad libitum-fed animals. This observation suggested that diet (apart from vitamin A) strongly influenced the activity of ATP sulphurylase. 2. Total starvation caused a severe decrease in activity in liver within 48hr. This was due to a lack of protein intake. 3. By feeding groups of vitamin A-deficient and pair-fed control rats on a diet containing 80% protein, the specific activity of the liver ATP sulphurylase was maintained in the pair-fed control group at the normal level of an ad libitum-fed rat, whereas it decreased by 25% (statistically significant at P<0.01) in the deficient rat. On a 20%-protein diet, there were no significant differences between vitamin A-deficient and pair-fed control rats. These relationships held also for enzyme activity expressed per g. of liver, per total liver and per g. of DNA. There were no differences in liver protein or DNA concentration between vitamin A-deficient and control rats on either protein intake. 4. Control rats on a 20%-protein diet had liver specific enzyme activities about one-half of those in control rats on an 80%-protein diet, as well as lower liver protein concentrations. 5. It is concluded that, when the effect of protein deprivation on ATP sulphurylase is separated from the effect of vitamin A deficiency, a lowering of the enzyme activity caused by the vitamin deficiency is demonstrable.