Proteinases in human cerebrospinal fluid

Abstract

Human cerebrospinal fluid was collected, concentrated and fractionated by DEAECM-cellulose and Sephadex G-100 chromatography. Proteinase activity was determined and this combined chromatography system made it possible to identify 3 proteinases. The pH optimum of one was 5.0, of the second 7.1 and of the third 8.0. Each proteinase had a different electrophoretic mobility. The molecular weight of the alkaline, i.e. kallikrein-type proteinase, was 27,000, that of the neutral 39,000 and that of the acid 74,000. As regards substrate specificity, both neutral and acid proteinase hydrolysed proteins, but the alkaline proteinase hydrolysed them extremely slowly and the proteinase activity possibly was derived from contamination. Neutral proteinase hydrolysed amide substrates of trypsin and also slowly ester substrates. Alkaline proteinase hydrolysed synthetic trypsin ester substrates extremely rapidly. Acid proteinase did not hydrolyse the synthetic substrates of trypsin at all and thus differed clearly from both the other proteinases in its substrate specificity. In their affector properties neutral and acid proteinase were so-called SH-enzymes and alkaline proteinase was activated by calcium. The other ions tested were not found in the concentrations used to have a definite influence on alkaline proteinase. On the other hand, alkaline proteinase resembled kallikrein fairly closely in the respect that it was inhibited by Limabean trypsin inhibitor which had no effect on the neutral and acid proteinases. The possible sources of origin of the enzymes and their properties were discussed in relation to other fluids of the organism and enzymes of the same type.