We would suggest a 50:50 mix of each enzyme's buffer. GluC works at maximal activity with a stimulating glutamic acid dipeptide in the reaction. Calcium chloride reduces autolysis of tryspin. Both buffers have a pH 8, Tris-HCI backbone. We have done our GluC/Trypsin digests this way with incubation overnight at 37°C. Neither enzyme is inhibited by the buffer mixing but they will, of course digest each other to some extent.