Previous data collection of the native enzyme to a resolution of 0.78 E provided the basis for the elucidation of the catalytic hydrogen in the active site of this serine protease. Follow up experiments are now being pursued to determine structures with different inhibitors and at different pH's with the goal of understanding the details of the mechanism of action of this class of enzymes. First diffraction data sets have been collected to resolutions of 0.8 and 0.84 E at two different pH's and the structures are now being refined.