Category:TP3

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(→‎Biosynthesis)
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{{Twocolumn|
 
{{Twocolumn|
 
The starting point is squalene, which is formed by joining two FPPs tail-to-tail.
 
The starting point is squalene, which is formed by joining two FPPs tail-to-tail.
−
In bacteria, squalene is cyclized via the 17α-deoxydammarenyl cation to hopene and other triterpenes.
+
Bacterial cyclases use squalene directly, but those of the other species use
−
In eukaryotes, 2,3-oxidosqualene is cyclized via the protosteryl cation to lanosterol or cycloartenol by a series of 1,2-hydride and methyl shifts (Wagner-Meerwein shifts).
+
2,3-oxidosqualene for cyclization.
−
Plant triterpenes arise from the dammarenyl cation.
+
  
−
 
+
* In bacteria, squalene is cyclized via the 17α-deoxydammarenyl cation to hopene and other triterpenes.
−
This molecule undergoes cyclization to form either the protosterol cation (through chair-boat cyclization) or the dammarenyl cation (through chair-chair cyclization).
+
* In eukaryotes, 2,3-oxidosqualene is cyclized via the protosteryl cation to lanosterol or cycloartenol by a series of 1,2-hydride and methyl shifts (Wagner-Meerwein shifts).
−
From the protosterol cation, lanosterol or cycloartenol occurs.
+
* In plants, various triterpenes arise from the dammarenyl cation.
−
From the 17β-dammarenyl cation, dammarane and other plant triterpenoids occur. From the 17α-damarenyl cation, hopanoids occur.
+
−
; animals, fungi, and yeast
+
−
: 2,3-oxidosqualene → lanosterol
+
−
; plants (including algae)
+
−
: 2,3-oxidosqualene → cycloartenol, dammarane
+
−
; bacteria
+
−
: 2,3-oxidosqualene → hopene
+
 
|
 
|
−
始まりとなる物質はスクアレンで、二分子のファルネシル二リン酸が末尾どうしで結合して作られます。
+
始まりとなる物質はスクアレンで、二分子のファルネシル二リン酸が末尾どうしで結合して作られます。バクテリアの環化酵素はスクアレンをそのまま利用しますが、それ以外の生物種では2,3-オキシドスクアレンを利用します。
  
−
バクテリアが合成するホパノイドはスクアレンがそのまま環化して生じ、
+
* バクテリアでは、スクアレンが環化して17α-ダンマラン型カチオンとなり、最終的にホペン他のトリテルペンになります。
 +
* 真核生物では、2,3-オキシドスクアレンが環化してプロトステロール型カチオンとなり、ラノステロールやシクロアルテノールになります。
 +
* 更に植物の場合、ダンマラン型のカチオンを経て様々なトリテルペンが生成されます。
 +
}}
  
−
2,3-オキシドスクアレンが環化する際に、ABC環が椅子-舟-5員環となる構造がまず生じ、椅子型C環へ拡張された後に5員型D環が生じたものがプロトステロールカチオン (椅子-舟-椅子-5員環) です。
 
−
このカチオンからメチル基の転位反応を経て （Wagner-Meerweinシフト）、ラノステロールおよびシクロアルテノール (ともに椅子-椅子-椅子-5員環) が生じます。
 
−
ダンマラン型の骨格は、2,3-オキシドスクアレンが環化する際に、椅子-椅子-椅子-5員環の構造がそのまま生じます。
 
−
ホパノイドは複雑で2回の環拡張をおこないます。
 
−
 
−
骨格転位反応　(Wagner-Meerwein shift) を起こし、種ごとに異なる前駆体を形成します。
 
−
; 動物、カビ、酵母
 
−
: 2,3-オキシドスクアレン → ラノステロール
 
−
; 植物 （および藻類）
 
−
: 2,3-オキシドスクアレン → シクロアルテノール、ダンマラン
 
−
; バクテリア
 
−
: 2,3-オキシドスクアレン → ホペン
 
−
}}
 
−
====Cyclization====
 
 
<center>
 
<center>
 
{|style="text-align:center"
 
{|style="text-align:center"
 +
|style="background-color:#ddf"| BACTERIA
 +
|
 +
|style="background-color:#fdd"| ANIMALS, FUNGI, and YEAST
 +
|style="background-color:#dfd"| PLANTS
 +
|-
 
| squalene
 
| squalene
 
|
 
|
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| lupeol [[Image:Arrow00dr35.png]] synthase
 
| lupeol [[Image:Arrow00dr35.png]] synthase
 
|-
 
|-
−
| deoxydammarenyl cation<br/>[[Image:Deoxydammarenyl cation.png]]
+
| 17&alpha;-deoxydammarenyl cation<br/>[[Image:Deoxydammarenyl cation.png]]
 
|
 
|
 
| protosteryl cation<br/>[[Image:Protosteryl cation.png]]
 
| protosteryl cation<br/>[[Image:Protosteryl cation.png]]
 
| dammarenyl cation<br/>[[Image:Dammarenyl cation.png]]
 
| dammarenyl cation<br/>[[Image:Dammarenyl cation.png]]
 
|-
 
|-
−
| [[Image:Arrow00d35.png]]
+
| D-ring [[Image:Arrow00d35.png]] expansion
 
|
 
|
−
| [[Image:Arrow00d35.png]]
+
| Wagner-[[Image:Arrow00d35.png]] Meerwein shift
−
| [[Image:Arrow00d35.png]]
+
| D-ring [[Image:Arrow00d35.png]] expansion
 
|-
 
|-
 
|[[Image:Hopyl cation.png]]
 
|[[Image:Hopyl cation.png]]
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| [[Image:Arrow00d35.png]]
 
| [[Image:Arrow00d35.png]]
 
|-
 
|-
−
| hopene<br/>[[Image:Hopene.png]]
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|style="background-color:#ddf"| hopene<br/>[[Image:Hopene.png]]
 
|
 
|
−
| lanosterol<br/>[[Image:Lanosterol.png]]
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|style="background-color:#fdd"| lanosterol<br/>[[Image:Lanosterol.png]]
−
| lupeol<br/>[[Image:Lupeol.png]]
+
|style="background-color:#dfd"| lupeol<br/>[[Image:Lupeol.png]]
 
|}
 
|}
  
 +
2,3-オキシドスクアレンが環化する際に、ABC環が椅子-舟-5員環となる構造がまず生じ、椅子型C環へ拡張された後に5員型D環が生じたものがプロトステロールカチオン (椅子-舟-椅子-5員環) です。
 +
このカチオンからメチル基の転位反応を経て （Wagner-Meerweinシフト）、ラノステロールおよびシクロアルテノール (ともに椅子-椅子-椅子-5員環) が生じます。
 +
ダンマラン型の骨格は、2,3-オキシドスクアレンが環化する際に、椅子-椅子-椅子-5員環の構造がそのまま生じます。
 +
ホパノイドは複雑で2回の環拡張をおこないます。
 
<ref>Ohyama K, Suzuki M, Kikuchi J, Saito K, Muranaka T “Dual biosynthetic pathways to phytosterol via cycloartenol and lanosterol in Arabidopsis” Proc Natl Acad Sci USA 106(3):725-730, 2009</ref>
 
<ref>Ohyama K, Suzuki M, Kikuchi J, Saito K, Muranaka T “Dual biosynthetic pathways to phytosterol via cycloartenol and lanosterol in Arabidopsis” Proc Natl Acad Sci USA 106(3):725-730, 2009</ref>
  

Revision as of 16:24, 5 August 2010

Contents

Triterpene (C30) Classes

Ring configuration

The basic structure is 4 carbon rings, cyclopenta[a]phenanthrene, gonane, or sterane. The rings B/C are always trans in all natural steroids. If the rings C/D are trans, it is called gonane. If its stereochemistry is unspecified, it is called sterane. Most steroids take gonane form, but in cardenolides and bufanolides, the rings C/D are cis.

Cyclopenta-a-phenanthrene.png Gonane.png
Cyclopenta[a]phenanthrene Gonane

The majority of steroids have methyl groups sticking out from the bridgehead positions C-10 and C-13. When these methyl groups (or hydrogens) stand above the plane, they are called β-configuration. Those below the plane are called α-configuration. If the configuration at any site is unknown, it is indicated as ξ (Greek Xi). By default, hydrogen atoms or substituents at the positions C-8, 9, 10, 13, and 14 are assumed to be 8β, 9α, 10β, 13β, and 14α configurations. C-5 is a special position, because there are as many 5α steroids as 5β are.

Cholestane.png 5alpha-steroid.png 5beta-steroid.png
cholestane backbone 5α-configuration 5β-configuration


Biosynthesis

The starting point is squalene, which is formed by joining two FPPs tail-to-tail. Bacterial cyclases use squalene directly, but those of the other species use 2,3-oxidosqualene for cyclization.

  • In bacteria, squalene is cyclized via the 17α-deoxydammarenyl cation to hopene and other triterpenes.
  • In eukaryotes, 2,3-oxidosqualene is cyclized via the protosteryl cation to lanosterol or cycloartenol by a series of 1,2-hydride and methyl shifts (Wagner-Meerwein shifts).
  • In plants, various triterpenes arise from the dammarenyl cation.

BACTERIA ANIMALS, FUNGI, and YEAST PLANTS
squalene 2,3-oxidosqualene
Squalene.png Arrow00r.png 2,3-oxidosqualene.png
squalene-hopene Arrow00d35.png cyclase lanosterol Arrow00dl35.png synthase lupeol Arrow00dr35.png synthase
17α-deoxydammarenyl cation
Deoxydammarenyl cation.png 		protosteryl cation
Protosteryl cation.png 		dammarenyl cation
Dammarenyl cation.png
D-ring Arrow00d35.png expansion Wagner-Arrow00d35.png Meerwein shift D-ring Arrow00d35.png expansion
Hopyl cation.png lanosteryl cation
Lanosteryl cation.png 		baccarenyl cation
Baccarenyl cation.png
Arrow00d35.png Arrow00d35.png Arrow00d35.png
hopene
Hopene.png 		lanosterol
Lanosterol.png 		lupeol
Lupeol.png

2,3-オキシドスクアレンが環化する際に、ABC環が椅子-舟-5員環となる構造がまず生じ、椅子型C環へ拡張された後に5員型D環が生じたものがプロトステロールカチオン (椅子-舟-椅子-5員環) です。 このカチオンからメチル基の転位反応を経て （Wagner-Meerweinシフト）、ラノステロールおよびシクロアルテノール (ともに椅子-椅子-椅子-5員環) が生じます。 ダンマラン型の骨格は、2,3-オキシドスクアレンが環化する際に、椅子-椅子-椅子-5員環の構造がそのまま生じます。 ホパノイドは複雑で2回の環拡張をおこないます。 [1]

Design of Tri-terpene ID numbers ID番号の設計

<center> 12-DIGIT

T P 3 x y y r h g n c c
x ... species information
Symbol at x Kingdom Phyla Examples
I Animalia Arthropoda (Insects, crabs) ecdysteroids
V Chordate (Vertebrates) sex steroids, corticosteroids, anabolic steroids
O Others marine steroids
P Plantae Phytosterols lanosterols, cholesterols, brassinolides
S Saponins saponins
F Fungi ergosterols ergosterols
B Bacteria bacterial sterols hopanoids
y ... backbone structure (母核構造) 
Symbol at y Carbons Steroids Backbone Structure
GN C17 gonane Gonane.png
ES C18 estrane Estrane.png
AD C19 androstane Androstane.png
PG C21 pregnane Pregnane.png
CA C24 cholane Cholane.png
CL C27 cholestane Cholestane.png
CM C28 campestane Campestane.png
EG C28 ergostane Ergostane.png
SG C29 (4 rings) stigmastane Stigmastane.png
PR C29 (4 rings) poriferastane Poriferastane.png
Symbol at y Carbons Triterpenoids Backbone Structure
PS C30 protostane Protostane.png
EU C30 euphane Euphane.png
LN C30 lanostane Lanostane.png
CY C30 cycloartane Cycloartane.png
FS C29 fusidane Fusidane.png
HP C30 (5 rings) hopane Hopane.png
FN C30 (5 rings) fernane Fernane.png
CC C30 cucurbitane Cucurbitane.png
DM C30 dammarane Dammarane.png
BC C30 baccharane Baccharane.png
HL C30 holostane Holostane.png
PF C29 (5 rings) pfaffane Pfaffane.png
LP C30 (5 rings) lupane Lupane.png
OL C30 (5 rings) oleanane Oleanane.png
FD C30 (5 rings) friedelane Friedelane.png
TR C30 (5 rings) taraxastane Taraxastane.png
UR C30 (5 rings) ursane Ursane.png
SR C30 (5 rings) serratane Serratane.png


r ... number of major rings (環構造数) 

Click above categories to see details.

h ... hydroxylation pattern (水酸基数) 

Click above categories to see details.

g ... glycosylation pattern(糖修飾パターン) 

Click above categories to see details.

n ... number of sugars (修飾糖数) 

Click above categories to see details.

c ... serial number (通し番号)

Cite error: <ref> tags exist, but no <references/> tag was found

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