b-Glucosidases such as (Zea mays) and Bgl4:1 (Brassica napus) have implicated roles in regulating plant development by releasing biologi-cally active cytokinins from O-glucosides. A key determinant of substrate specificity in is the F193–F200–W373–F461 cluster. However, despite sharing the same substrates, amino acids in the active sites of and Bgl4:1 differ dramatically.