THE EFFECTS OF PHOSPHOPROTEINS ON ACID BALANCE IN NORMAL SUBECTS*

Abstract

Large supplements of purified soy phosphoprotein and of beefsteak were fed to normal subjects and the effects on acid balance compared. The soy protein generated 3.9 meq of acid per g of N and the beefsteak 2.9 meq per g N. The results show that a significant fraction of the net endogenous acid produced from the metabolism of the soy protein was predictably related to its phosphorus content, but no such sources of acid could be demonstrated from meat. It is suggested that the production of acid associated with the presence of phosphate groups in a protein will be determined both by the structural relationships of the phosphate and the nature of the associated cations. The remainder of the acid production from the soy phosphoprotein and all of the acid arising from the meat was accounted for by increased oxidation of sulfur and increased endogenous production of organic acids.