Kallikrein Phenotyping by Isoelectric Focusing

Abstract

The influence of kallikrein on the coagulation and the fibrinolytic system depends on the reciprocal activation with factor XII. The inactive prekal1ikrein exists as a single polypeptide chain of 619 amino acids with a molecular weight of 85.000. Activation by factor XII a is achieved by the cleavage of an internal Arg-Ile bond. Plasma kallikrein is then composed of a heavy chain (371 amino acids) and light chain (248 amino acids) held together by disulfide bonds (1, 4, 5, 6). The aminoacid sequence of human plasma prekal1ikrein shows 58% identity with factor XI (2, 3). The heavy chain is composed of repeated sequences homologous to factor XI. The light chain contains the catalytic part of the en- zym and is homologous to the trypsin family of the serine proteases (1). In plasma prekal1ikrein circulates in a complex with high MW kininogen (5). The normal plasma concentration is 50pg/ml. Prekal1ikrein deficiency causes abnormalities in the coagulation, fibrinolytic, complement and kinin systems (7). Several different kallikrein genes are found. The nucleotid sequences show homologies (10). Several DNA polymorphisms in the kallikrein genes are observed (11). The human renal kallikrein and prostate specific antigen (PSA) genes were localized to chromosome 19q13 (8, 9).