Squalene-hopene cyclase: final deprotonation reaction, conformational analysis for the cyclization of (3R,S)-2,3-oxidosqualene and further evidence for the requirement of an isopropylidene moiety both for initiation of the polycyclization cascade and for the formation of the 5-membered E-ring.
To provide insight into the polycyclization mechanism of squalene by squalene-hopene cyclase (SHC) from Alicyclobacilus acidocaldarius, some analogs of nor- and bisnorsqualenes were synthesized including the deuterium-labeled squalenes and incubated with the wild-type SHC, leading to the following inferences. (1) The deprotonation reaction for the introduction of the double bond of the hopene skeleton occurs exclusively from the Z-methyl group on the terminal double bond of squalene. (2) 3R-Oxidosqualene was folded in a boat conformation for the A-ring construction, while the 3S-form was in a chair structure. (3) The terminal two methyl groups are indispensable both for the formation of the 5-membered E-ring of the hopene skeleton and for the initiation of the polycyclization cascade, but the terminal Z-methyl group has a more crucial role for the construction of the 5-membered E-ring than the E-methyl group. (4) Some of the novel terpene skeletons, 36, 37, 39 and 40, were created from the analogs employed in this investigation.
Hoshino
Tsutomu
T
Department of Applied Biological Chemistry, Faculty of Agriculture, and Graduate School of Science and Technology, Niigata University, Ikarashi, Niigata 950-2181, Japan. hoshitsu@agr.niigata-u.ac.jp
Nakano
Schin-ichi
S
Kondo
Tomohiro
T
Sato
Tsutomu
T
Miyoshi
Aya
A
D000475:Alkenes / Q000737:chemistry; D001665:Binding Sites / Q000502:physiology; D001952:Bridged-Ring Compounds / Q000737:chemistry / Q000378:metabolism; D002849:Chromatography, Gas; D003500:Cyclization; D003903:Deuterium / Q000737:chemistry; D006094:Gram-Positive Bacteria / Q000201:enzymology; D019751:Intramolecular Transferases / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D011083:Polycyclic Compounds / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013185:Squalene / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014315:Triterpenes / Q000737:chemistry* / Q000378:metabolism; D014867:Water / Q000737:chemistry
C002821:2,3-oxidosqualene; D000475:Alkenes; D001952:Bridged-Ring Compounds; D011083:Polycyclic Compounds; D011994:Recombinant Proteins; D014315:Triterpenes; D014867:Water; C028765:diploptene; D013185:Squalene; D003903:Deuterium; C013658:propylene; D019751:Intramolecular Transferases; C066630:squalene-hopene cyclase