Expression, purification, crystallization and preliminary X-ray analysis of strictosidine glucosidase, an enzyme initiating biosynthetic pathways to a unique diversity of indole alkaloid skeletons

Strictosidine β-d-glucosidase, a plant enzyme initiating biosynthetic pathways to about 2000 monoterpenoid indole alkaloids with an extremely large number of various carbon skeletons, has been functionally expressed in Escherichia coli and purified to homogeneity in mg scale. Crystals suitable for X-ray analysis were found by robot-mediated screening. Using the hanging-drop technique, optimum conditions were 0.3 M ammonium sulfate, 0.1 M sodium acetate, pH 4.6 and PEG 4000 (10%) as precipitant buffer. The crystals of strictosidine glucosidase belong to the space group P4212 with unit cell dimensions of a=157.63, c=103.59 Å and diffract X-rays to 2.48-Å resolution.