Studies of an abnormal serum albumin unstable upon storage

A case of inherited bisalbuminemia was discovered in which electrophoretic controls showed that the proportion of the abnormal albumin decreased progressively during storage of the serum either at 4 degrees C or at room temperature. Such a decrease was also found when the serum was incubated with the proteolytic enzymes trypsin or plasmin. Studies with the isolated abnormal albumin showed that either during storage or after incubation with trypsin (or plasmin), its mobility became identical to that of normal serum albumin. Structural analyses showed that the albumin variant was identical to the previously described pro-albumin Christchurch that contains an additional N-terminal sequence: Arg-Gly-Val-Phe-Arg-Gln. It was therefore suggested that the progressive decrease of the abnormal albumin during storage by serum was related to the cleavage of the N-terminal abnormal sequence by plasmin already present in the serum. The decrease of the abnormal albumin during storage was inhibited by addition of cortisol to serum (1 mol per mol serum albumin). This was found related to a protective effect of cortisol bound to the albumin variant on proteolysis by plasmin.