Partial purification and characterization of a trypsin-like proteinase from rabbit preimplantation uterine fluid.

Previous investigations have proved that proteinases are involved in implantation of the rabbit embryo into the uterine tissues. This study describes a trypsin-like enzyme found in the blastocyst fluid and uterine flushings at the time of implantation. The proteinase isolated from uterine flushings has a molecular mass of about 50 kDa and exists in two differently charged forms of pI 4.0 and 4.5. Tests with low molecular mass 4-nitroanilide substrates proved a marked cleavage selectivity of the enzyme for arginyl bonds. The catalytic activity is not affected by Ca2+ and EDTA but inhibited by aprotinin and a high concentration (10(-6)M) of lima bean trypsin inhibitor.