
doi: 10.1039/b823167b
pmid: 19343258
The enzymatic cyclization reaction of polyprenoid C(33) by squalene-hopene cyclase (SHC) was investigated with the intention of creating an unnatural hexacyclic compound. The enzymatic products consisted of mono-, bi-, tri-, tetra- and pentacyclic skeletons; however, hexacyclic products were not generated, contrary to our expectations. The absence of a hexacyclic skeleton indicated that the entire carbon chain of C(33) polyprene could not be included in the reaction cavity. Formation mechanisms of the products having mono- to pentacycles were discussed. Both chair/chair/boat conformation and chair/chair/chair conformations were formed for a tricycle, and both chair/chair/chair/boat conformation and chair/chair/chair/chair structures were constructed for a tetracycle. The pentacyclic product was created from the chair/chair/chair/chair/boat conformation. Squalene was folded in an all pre-chair conformation inside the reaction cavity to form the hopene skeleton. Therefore, the formation of a boat structure during the polycyclization reaction indicated that the molecule of polyprene C(33) was folded improperly due to incorrect arrangement/positioning in the reaction cavity. The creation of the hexacyclic core failed; however, it should be noted that SHC possessed great potential to tolerate the elongated squalene analog C(33), thus leading to the creation of novel compounds with C(33).
Squalene, Chromatography, Gas, Bacterial Proteins, Molecular Structure, Cyclization, Escherichia coli, Stereoisomerism, Intramolecular Transferases, Recombinant Proteins
Squalene, Chromatography, Gas, Bacterial Proteins, Molecular Structure, Cyclization, Escherichia coli, Stereoisomerism, Intramolecular Transferases, Recombinant Proteins
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