Lactone-forming carboxylesterase, specifically catalyzing intramolecular transesterification, but not hydrolysis. Involved in the biosynthesis of tulipalins, defensive chemicals that show antimicrobial activities against a broad range of strains of bacteria and fungi. Substrates are 6-tuliposide B > 6-tuliposide A. 6-tuliposide B = D-glucose + tulipalin B Inhibited by Ag(+), Cu(2+), Fe(2+), Hg(2+), V(3+) and phenylmethylsulfonyl fluoride (PMSF). kcat is 8.7 sec(-1) with 6-tuliposide A as substrate. kcat is 2000 sec(-1) with 6-tuliposide B as substrate. Optimum pH is 7.0-7.5. Optimum temperature is 30-40 degrees Celsius. Homodimer. Expressed in the pollen grains. Not glycosylated. Belongs to the AB hydrolase superfamily.