I would suggest a 50:50 mix of the two buffers. GluC likes to have the stimulating E-E dipeptide present for maximal activity. Trypsin is stabilized by the calcium chloride, which reduces autolysis. Tris-HCl is present in both buffers at pH 8, so mixing the two buffers presents no problem such as altering the pH. We have done our GluC/Trypsin double digests this way with incubation overnight at 25-37 C. Nether enzyme is inhibited by the buffer mix but they will, of course, digest each other to some extent.