AN ISOFORM OF PLASMA KALLIKREIN OCCURRING IN THE FOLLICULAR-FLUID OF HUMAN OVARIES

Follicular fluid obtained from follicle aspirates of women participati ng in in vitro fertilization program was found to contain a proteinase whose properties were very similar to those of plasma kallikrein, but behaved differently in ion exchange column chromatographies. The enzy me was purified to apparent homogeneity and characterized. The molecul ar weight of the enzyme was estimated to be 87,000 in sodium dodecyl s ulfate-polyacrylamide gel electrophoresis, and 80,000 in gel filtratio n on a Sephacryl S-200 column. The values were slightly smaller than t hose (90,000 in SDS-PAGE and 89,000 in the gel filtration under the sa me conditions) of plasma kallikrein. The enzyme resembled plasma kalli krein in substrate specificity, susceptibility to various proteinase i nhibitors, and reactivity to anti-human plasma kallikrein antibody. Ba sed on these results, we tentatively conclude that the enzyme is an is oform of plasma kallikrein.