EC 2.5.1.67     
Accepted name: chrysanthemyl diphosphate synthase
Reaction: 2 prenyl diphosphate = diphosphate + chrysanthemyl diphosphate
Glossary: chrysanthemyl = [2,2-dimethyl-3-(2-methylprop-1-en-1-yl)cyclopropyl]methyl
chrysanthemic acid = 2,2-dimethyl-3-(2-methylprop-1-en-1-yl)cyclopropane-1-carboxylic acid
Other name(s): CPPase; dimethylallyl-diphosphate:dimethylallyl-diphosphate dimethylallyltransferase (chrysanthemyl-diphosphate-forming)
Systematic name: prenyl-diphosphate:prenyl-diphosphate prenyltransferase (chrysanthemyl-diphosphate-forming)
Comments: Requires a divalent metal ion for activity, with Mg2+ being better than Mn2+ [1]. Chrysanthemyl diphosphate is a monoterpene with a non-head-to-tail linkage. It is unlike most monoterpenoids, which are derived from geranyl diphosphate and have isoprene units that are linked head-to-tail. The mechanism of its formation is similar to that of the early steps of squalene and phytoene biosynthesis. Chrysanthemyl diphosphate is the precursor of chrysanthemic acid, the acid half of the pyrethroid insecticides found in chrysanthemums.
References:
1.  Rivera, S.B., Swedlund, B.D., King, G.J., Bell, R.N., Hussey, C.E., Jr., Shattuck-Eidens, D.M., Wrobel, W.M., Peiser, G.D. and Poulter, C.D. Chrysanthemyl diphosphate synthase: isolation of the gene and characterization of the recombinant non-head-to-tail monoterpene synthase from Chrysanthemum cinerariaefolium. Proc. Natl. Acad. Sci. USA 98 (2001) 4373–4378. [PMID: 11287653]
2.  Erickson, H.K. and Poulter, C.D. Chrysanthemyl diphosphate synthase. The relationship among chain elongation, branching, and cyclopropanation reactions in the isoprenoid biosynthetic pathway. J. Am. Chem. Soc. 125 (2003) 6886–6888. [PMID: 12783539]
[EC 2.5.1.67 created 2007]
 
 
EC 2.5.1.69     
Accepted name: lavandulyl diphosphate synthase
Reaction: 2 prenyl diphosphate = diphosphate + lavandulyl diphosphate
Glossary: lavandulyl = 5-methyl-2-(prop-1-en-2-yl)hex-4-en-1-yl
Other name(s): FDS-5; dimethylallyl-diphosphate:dimethylallyl-diphosphate dimethylallyltransferase (lavandulyl-diphosphate-forming)
Systematic name: prenyl-diphosphate:prenyl-diphosphate prenyltransferase (lavandulyl-diphosphate-forming)
Comments: Lavandulyl diphosphate is a monoterpene with a non-head-to-tail linkage. It is unlike most monoterpenoids, which are derived from geranyl diphosphate and have isoprene units that are linked head-to-tail. When this enzyme is incubated with prenyl diphosphate and 3-methylbut-3-en-1-yl diphosphate, it also forms the regular monoterpene geranyl diphosphate [2]. The enzyme from Artemisia tridentata (big sagebrush) forms both lavandulyl diphosphate and chrysanthemyl diphosphate (see EC 2.5.1.67, chrysanthemyl diphosphate synthase) when prenyl diphosphate is the sole substrate.
References:
1.  Erickson, H.K. and Poulter, C.D. Chrysanthemyl diphosphate synthase. The relationship among chain elongation, branching, and cyclopropanation reactions in the isoprenoid biosynthetic pathway. J. Am. Chem. Soc. 125 (2003) 6886–6888. [PMID: 12783539]
2.  Hemmerlin, A., Rivera, S.B., Erickson, H.K. and Poulter, C.D. Enzymes encoded by the farnesyl diphosphate synthase gene family in the Big Sagebrush Artemisia tridentata ssp. spiciformis. J. Biol. Chem. 278 (2003) 32132–32140. [PMID: 12782626]
[EC 2.5.1.69 created 2007]