Cathepsins B1 from human fetal membranes.

Cathepsins B1 (EC 3.4.22.1) were isolated from fetal membranes of human placenta, i.e. amnion and chorion-decidua. Purification of the enzymes was achieved by the freezing-thawing technique, ammonium sulphate fractionation and Sephadex gel filtration. Cathepsis B1 separated either from amnion or from chorion-decidua exhibited optimum activity at pH 6.2, and an optimum temperature between 42-45 degrees C. They were inhibited by heavy metals, and compounds which react with the thiol groups. Isoelectric focusing demonstrated three isoenzymes of cathepsin B1 originating from chorion-decidua, while only one band was found for the enzyme from amnion.