Albumin possesses intrinsic enolase activity towards dihydrotestosterone which can differentiate benign from malignant breast tumors

Serum albumin was found to possess enolase activity towards the dihydrotest esterone (DHT) molecule, converting it from its 3-keto to 3-enol form. This activity was accompanied by albumin during all stages of purification, as well as following various treatments, a fact indicating that the enzymatic activity was an intrinsic property of albumin molecule and did not represen t an impurity of the preparation. Enolase activity was decreased in paralle l with the quantity of intact albumin molecules when proteolytic enzymes we re used for their degradation. The activity was strongly inhibited by Ni (I I) and Cu (II) ions, which bind to 3-histidine of the albumin molecule, as well as by oleic acid and cholesterol. It was also inhibited, in a reversib le mantle, by surface - active agents. Enolase activity was found in all ma mmalian,species studied the specific activity however was very low in the s e, nm of dogs. The administration of DHT to mice did not influence the albu min or enolase levels in their serum. The optimum pH of enolase was at 9.2, with a carbonate buffer solution. In addition to the serum, enolase activi ty was found to be a feature of intracellular, albumin. The two albumins ex hibited the same specific activity and the same Km for DHT. The study of cy tosolic albumin, obtained from human mammary gland tissue, revealed that be nign and malignant tumors of this gland differed substantially with respect to their percentage of albumin. Significant differences were also observed in enolase activity, a consequence of the existence of a fraction of album in in the malignant tissue in a polymeric form. This form exhibited a decre ased enzymatic activity, compared to its monomeric form, exclusively encoun tered in benign breast specimens. The last observation, along with the quan titative reliable differentiation between benign and malignant breast tumor s.