THE HIGH ALKALINE FRACTION ON ISOELECTRIC-FOCUSING OF CEREBROSPINAL-FLUID IS CYSTATIN-C

A high alkaline fraction with a pi of 9.2 is sometimes seen on isoelec tric focusing patterns of cerebrospinal fluid. The appearance of this fraction mainly depends on the type of concentrators used to prepare t he cerebrospinal fluid samples, prior to isoelectric focusing. The ami no acid sequence of the high alkaline fraction showed sequence identit y to cystatin C, a cysteine protease inhibitor with a pi of 9.2-9.3 an d a molecular mass of 13.4 kDa. In addition, on Western blot the high alkaline fraction was recognized by an antibody, directed against cyst atin C. Taken together, the present findings demonstrate that the high alkaline fraction is cystatin C. (C) 1998 Elsevier Science B.V.