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'''Momilactone B''' is an [[allelopathic]] agent produced from the roots of rice ([[Oryza sativa|''Oryza sativa'' L.]]) (100&nbsp;mg from 200&nbsp;kg dry rice husk) <ref name=momilactone_B_isolation>{{cite journal | author=Kato, T.; Kabuto, C.; Sasaki, N.; Tsunagawa, M.; Aizawa, H.; Fujita, K.; Kato, Y.; Kitahara, Y. |title=Momilactones, Growth Inhibitors from Rice, Oryza Sativa L. | journal=Tet. Lett. | year=1973 | volume=14 | issue=39 | pages=3861–3864 | doi= 10.1016/S0040-4039(01)87058-1}}</ref>. It has been shown to be produced in high concentrations by the roots of rice seedlings <ref name=production_paper>{{cite journal | author=Toyomasu, T.; Kagahara, T.; Okada, K.; Koga, J.; Hasegawa, M.; Mitsuhashi, W.; Sassa, T.; Yamane, H. |title=Diterpene Phytoalexins are Biosynthesized in and Exuded from the Roots of Rice Seedlings | journal=Biosci. Biotechnol. Biochem. | year=2008 | volume=72 | issue=2 | pages=562–567 | doi= 10.1271/bbb.70677}}</ref>. The production of momilactone B has also been induced in response to infection by [[Magnaporthe grisea|blast fungus]] ([[Magnaporthe grisea|Pyricularia oryzae]]) or irradiated with [[Ultraviolet|UV light]]<ref name=momilactone_B_induced_production>{{cite journal | author=Cartwright, D. W.; Langcake, P.; Pryce, R. J.; Leworthy, D. P.; Ride, J. P. |title=Isolation and Characterization of Two Phytoalexins from Rice as Momilactones A and B | journal=Phytochemistry | year=1981 | volume=20 | issue=3 | pages=535–537 | doi= 10.1016/S0031-9422(00)84189-8}}</ref>. More recently is has been shown to be a potential [[Chemotherapy|chemotherapeutic agent]] against [[Colorectal cancer|human colon cancer]]<ref name=cytotoxic_activity>{{cite journal | author=Kim, S.; Park, H.; Park, E.; Lee, S. |title=Cytotoxic and Antitumor Activity of Momilactone B from Rice Hulls | journal=J. Agric. Food Chem. | year=2007 | volume=55 | issue=5 | pages=1702–1706 | doi= 10.1021/jf062020b}}</ref>.
'''Momilactone B''' is an [[allelopathic]] agent produced from the roots of rice ([[Oryza sativa|''Oryza sativa'' L.]]) (100&nbsp;mg from 200&nbsp;kg dry rice husk) <ref name=momilactone_B_isolation>{{cite journal | author=Kato, T.; Kabuto, C.; Sasaki, N.; Tsunagawa, M.; Aizawa, H.; Fujita, K.; Kato, Y.; Kitahara, Y. |title=Momilactones, Growth Inhibitors from Rice, Oryza Sativa L. | journal=Tet. Lett. | year=1973 | volume=14 | issue=39 | pages=3861–3864 | doi= 10.1016/S0040-4039(01)87058-1}}</ref>. It has been shown to be produced in high concentrations by the roots of rice seedlings <ref name=production_paper>{{cite journal | author=Toyomasu, T.; Kagahara, T.; Okada, K.; Koga, J.; Hasegawa, M.; Mitsuhashi, W.; Sassa, T.; Yamane, H. |title=Diterpene Phytoalexins are Biosynthesized in and Exuded from the Roots of Rice Seedlings | journal=Biosci. Biotechnol. Biochem. | year=2008 | volume=72 | issue=2 | pages=562–567 | doi= 10.1271/bbb.70677 | pmid=18256463}}</ref>. The production of momilactone B has also been induced in response to infection by [[Magnaporthe grisea|blast fungus]] ([[Magnaporthe grisea|Pyricularia oryzae]]) or irradiated with [[Ultraviolet|UV light]]<ref name=momilactone_B_induced_production>{{cite journal | author=Cartwright, D. W.; Langcake, P.; Pryce, R. J.; Leworthy, D. P.; Ride, J. P. |title=Isolation and Characterization of Two Phytoalexins from Rice as Momilactones A and B | journal=Phytochemistry | year=1981 | volume=20 | issue=3 | pages=535–537 | doi= 10.1016/S0031-9422(00)84189-8}}</ref>. More recently is has been shown to be a potential [[Chemotherapy|chemotherapeutic agent]] against [[Colorectal cancer|human colon cancer]]<ref name=cytotoxic_activity>{{cite journal | author=Kim, S.; Park, H.; Park, E.; Lee, S. |title=Cytotoxic and Antitumor Activity of Momilactone B from Rice Hulls | journal=J. Agric. Food Chem. | year=2007 | volume=55 | issue=5 | pages=1702–1706 | doi= 10.1021/jf062020b | pmid=17326606}}</ref>.


==Biosynthesis==
==Biosynthesis==
Of the natural products isolated from rice, fifteen have been shown to be [[phytoalexins]]. Of these fifteen, fourteen, including momilactone B, are [[Terpene|diterpenes]] commonly [[Biosynthesis|biosynthesized]] from [[geranylgeranyl diphosphate]] ([[Geranylgeranyl pyrophosphate|GGDP]]).
Of the natural products isolated from rice, fifteen have been shown to be [[phytoalexins]]. Of these fifteen, fourteen, including momilactone B, are [[Terpene|diterpenes]] commonly [[Biosynthesis|biosynthesized]] from [[geranylgeranyl diphosphate]] ([[Geranylgeranyl pyrophosphate|GGDP]]).
[[Image:GGDP.png|thumb|left|Figure 1. Geranylgeranyl diphosphate]]
[[Image:GGDP.png|thumb|left|Figure 1. Geranylgeranyl diphosphate]]
The first step in the [[biosynthesis]] of momilactone B is the [[Cyclic compound|cyclization]] of [[Geranylgeranyl pyrophosphate|GGDP]] to ''syn''-copalyl diphosphate (''syn''-CDP), a type B [[Cyclic compound|cyclization]]. This is initiated by the addition of a [[proton]] to the terminal [[Alkene|olefin]] bond of [[Geranylgeranyl pyrophosphate|GGDP]]. The [[genes]] encoding for ''syn''-CDP [[synthase]] was found by Otomo ''et al.''. in 2004<ref name=Type_B_Cyclase>{{cite journal | author=Otomo, K.; Kenmoku, H.; Oikawa, H.; König, W. A.; Toshima, H.; Mitsuhashi, W.; Yamane, H.; Sassa, T.; Toyomasu, T. |title=Biological functions of ''ent''- and ''syn''-copalyl diphosphate synthases in rice: key enzymes for the branch point of gibberellin and phytoalexin biosynthesis | journal=Plant J. | year=2004 | volume=39 | issue=6 | pages=886–893 | doi= 10.1111/j.1365-313X.2004.02175.x}}</ref>. This was labeled as ''OsCyc''1 (''Oryza sativa Cyclase'' 1). According to the rice genome database, ''OsCyc1'' corresponds to ''OsCPS''4 (AL662933) found in [[chromosome| chromosome 4]] (14.3cM) discovered by Sakamoto ''et al.''. in 2004<ref name=Gene_correspondence>{{cite journal | author=Sakamoto, T.; Miura, K.; Itoh, H.; Tatsumi, T.; Ueguchi-Tanaka, M.; Ishiyama, K.; Kobayashi, M.; Agrawal, G. K.; Takeda, S.; Abe, K.; Miyao, A.; Hirochika, H.; Kitano, H.; Ashikari, M.; Matsuoka, M. |title=An Overview of Gibberellin Metabolism Enzyme Genes and Their Related Mutants in Rice | journal=Plant Phys. | year=2004 | volume=134 | issue=4 | pages=1642–1653}}</ref>.
The first step in the [[biosynthesis]] of momilactone B is the [[Cyclic compound|cyclization]] of [[Geranylgeranyl pyrophosphate|GGDP]] to ''syn''-copalyl diphosphate (''syn''-CDP), a type B [[Cyclic compound|cyclization]]. This is initiated by the addition of a [[proton]] to the terminal [[Alkene|olefin]] bond of [[Geranylgeranyl pyrophosphate|GGDP]]. The [[genes]] encoding for ''syn''-CDP [[synthase]] was found by Otomo ''et al.''. in 2004<ref name=Type_B_Cyclase>{{cite journal | author=Otomo, K.; Kenmoku, H.; Oikawa, H.; König, W. A.; Toshima, H.; Mitsuhashi, W.; Yamane, H.; Sassa, T.; Toyomasu, T. |title=Biological functions of ''ent''- and ''syn''-copalyl diphosphate synthases in rice: key enzymes for the branch point of gibberellin and phytoalexin biosynthesis | journal=Plant J. | year=2004 | volume=39 | issue=6 | pages=886–893 | doi= 10.1111/j.1365-313X.2004.02175.x | pmid=15341631}}</ref>. This was labeled as ''OsCyc''1 (''Oryza sativa Cyclase'' 1). According to the rice genome database, ''OsCyc1'' corresponds to ''OsCPS''4 (AL662933) found in [[chromosome| chromosome 4]] (14.3cM) discovered by Sakamoto ''et al.''. in 2004<ref name=Gene_correspondence>{{cite journal | author=Sakamoto, T.; Miura, K.; Itoh, H.; Tatsumi, T.; Ueguchi-Tanaka, M.; Ishiyama, K.; Kobayashi, M.; Agrawal, G. K.; Takeda, S.; Abe, K.; Miyao, A.; Hirochika, H.; Kitano, H.; Ashikari, M.; Matsuoka, M. |title=An Overview of Gibberellin Metabolism Enzyme Genes and Their Related Mutants in Rice | journal=Plant Phys. | year=2004 | volume=134 | issue=4 | pages=1642–1653}}</ref>.
[[Image:Type B Cyclase.png|center|800px|Figure 2. [[Geranylgeranyl pyrophosphate|GGDP]] cyclization to ''syn''-CDP]]
[[Image:Type B Cyclase.png|center|800px|Figure 2. [[Geranylgeranyl pyrophosphate|GGDP]] cyclization to ''syn''-CDP]]
The second step is the [[cyclization]] of ''syn''-CDP to 9β-pimara-7,15-diene. This step is initiated by the [[Elimination reaction|elimination]] of the [[diphosphate|diphosphate group]], a type A [[cyclization]]. The [[genes]] encoding for the type A [[cyclase]] were found by Otomo ''et al.''. in 2004<ref name=Type_A_Cyclase>{{cite journal | author=Otomo, K.; Kanno, Y.; Motegi, A.; Kenmoku, H.; Yamane, H.; Mitsuhashi, W.; Oikawa, H.; Toshima, H.; Itoh, H.; Matsuoka, M.; Sassa, T.; Toyomasu, T. |title=Diterpene Cyclases Responsible for the Biosynthesis of Phytoalexins, Momilactones A, B, and Oryzalexins A-F in Rice | journal=Biosci. Biotechnol. Biochem. | year=2004 | volume=68 | issue=9 | pages=2001–2006 | doi= 10.1271/bbb.68.2001}}</ref>. It is suggested that ''OsKS''4, located on [[chromosome|chromosome 4]] (14.3cM) is one of the [[genes]] responsible for [[phytoalexin]] [[biosynthesis]]. After [[UV-radiation]], ''OsKS''4 mRNA levels rise drastically in response to the attack.
The second step is the [[cyclization]] of ''syn''-CDP to 9β-pimara-7,15-diene. This step is initiated by the [[Elimination reaction|elimination]] of the [[diphosphate|diphosphate group]], a type A [[cyclization]]. The [[genes]] encoding for the type A [[cyclase]] were found by Otomo ''et al.''. in 2004<ref name=Type_A_Cyclase>{{cite journal | author=Otomo, K.; Kanno, Y.; Motegi, A.; Kenmoku, H.; Yamane, H.; Mitsuhashi, W.; Oikawa, H.; Toshima, H.; Itoh, H.; Matsuoka, M.; Sassa, T.; Toyomasu, T. |title=Diterpene Cyclases Responsible for the Biosynthesis of Phytoalexins, Momilactones A, B, and Oryzalexins A-F in Rice | journal=Biosci. Biotechnol. Biochem. | year=2004 | volume=68 | issue=9 | pages=2001–2006 | doi= 10.1271/bbb.68.2001 | pmid=15388982}}</ref>. It is suggested that ''OsKS''4, located on [[chromosome|chromosome 4]] (14.3cM) is one of the [[genes]] responsible for [[phytoalexin]] [[biosynthesis]]. After [[UV-radiation]], ''OsKS''4 mRNA levels rise drastically in response to the attack.
[[Image:Type A Cyclase.png|center|600px|Figure 3. ''syn''-CDP cyclization to 9β-pimara-7,15-diene]]
[[Image:Type A Cyclase.png|center|600px|Figure 3. ''syn''-CDP cyclization to 9β-pimara-7,15-diene]]
Further [[oxidation]] of the 9β-pimara-7,15-diene compound followed by [[lactone]] and [[lactol]] formation yields momilactone B. Though the [[gene sequence]] of these [[oxidation]]s is unknown, [[P450|P450 monooxygenase genes]] have been identified near the [[cyclase]] [[genes]] on [[chromosome|chromosome 4]]. This suggests that the complete [[gene cluster]] for the [[biosynthesis]] of momilactone B is located on [[chromosome|chromosome 4]] of rice.
Further [[oxidation]] of the 9β-pimara-7,15-diene compound followed by [[lactone]] and [[lactol]] formation yields momilactone B. Though the [[gene sequence]] of these [[oxidation]]s is unknown, [[P450|P450 monooxygenase genes]] have been identified near the [[cyclase]] [[genes]] on [[chromosome|chromosome 4]]. This suggests that the complete [[gene cluster]] for the [[biosynthesis]] of momilactone B is located on [[chromosome|chromosome 4]] of rice.

Revision as of 00:21, 12 May 2010

Momilactone B
File:Momilactone B.png
Names
IUPAC name
4H-3,10b-Ethano-1H,3H-benzo(f)furo(4,3,2-de)-2-benzopyran-4-one, 8-ethenyl-3a,5a,7,8,9,10,10a,10c-octahydro-3a,8-dimethyl-, (3S-(3alpha,3abeta,5abeta,8alpha,10aalpha,10bbeta,10cbeta))-
Identifiers
Properties
C20H26O4
Molar mass 330.4180 g/mol
Melting point 242 °C (468 °F; 515 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Momilactone B is an allelopathic agent produced from the roots of rice (Oryza sativa L.) (100 mg from 200 kg dry rice husk) [1]. It has been shown to be produced in high concentrations by the roots of rice seedlings [2]. The production of momilactone B has also been induced in response to infection by blast fungus (Pyricularia oryzae) or irradiated with UV light[3]. More recently is has been shown to be a potential chemotherapeutic agent against human colon cancer[4].

Biosynthesis

Of the natural products isolated from rice, fifteen have been shown to be phytoalexins. Of these fifteen, fourteen, including momilactone B, are diterpenes commonly biosynthesized from geranylgeranyl diphosphate (GGDP).

Figure 1. Geranylgeranyl diphosphate

The first step in the biosynthesis of momilactone B is the cyclization of GGDP to syn-copalyl diphosphate (syn-CDP), a type B cyclization. This is initiated by the addition of a proton to the terminal olefin bond of GGDP. The genes encoding for syn-CDP synthase was found by Otomo et al.. in 2004[5]. This was labeled as OsCyc1 (Oryza sativa Cyclase 1). According to the rice genome database, OsCyc1 corresponds to OsCPS4 (AL662933) found in chromosome 4 (14.3cM) discovered by Sakamoto et al.. in 2004[6].

Figure 2. GGDP cyclization to syn-CDP
Figure 2. GGDP cyclization to syn-CDP

The second step is the cyclization of syn-CDP to 9β-pimara-7,15-diene. This step is initiated by the elimination of the diphosphate group, a type A cyclization. The genes encoding for the type A cyclase were found by Otomo et al.. in 2004[7]. It is suggested that OsKS4, located on chromosome 4 (14.3cM) is one of the genes responsible for phytoalexin biosynthesis. After UV-radiation, OsKS4 mRNA levels rise drastically in response to the attack.

Figure 3. syn-CDP cyclization to 9β-pimara-7,15-diene
Figure 3. syn-CDP cyclization to 9β-pimara-7,15-diene

Further oxidation of the 9β-pimara-7,15-diene compound followed by lactone and lactol formation yields momilactone B. Though the gene sequence of these oxidations is unknown, P450 monooxygenase genes have been identified near the cyclase genes on chromosome 4. This suggests that the complete gene cluster for the biosynthesis of momilactone B is located on chromosome 4 of rice.

Figure 4. Oxidation of 9β-pimara-7,15-diene to Momilactone B
Figure 4. Oxidation of 9β-pimara-7,15-diene to Momilactone B

Further research is being done on isolating the enzymes responsible for the biosynthesis of momilactone B and other phytoalexins found in rice. Once these enzymes are found, the stereochemistry of these reactions could be examined. Further studies into the biosynthesis of momilactone B could prove useful in studying the defense mechanisms of rice.

Stereochemistry

Please note: the stereochemistry determined by Kato et al..[1] is different than that shown in the biosynthesis references. The stereochemistry of momilactone B shown here is based on the biosynthesis references [5],[6],[7]. There are no known papers correcting the stereochemistry from the isolation paper[1].

References

  1. ^ a b c Kato, T.; Kabuto, C.; Sasaki, N.; Tsunagawa, M.; Aizawa, H.; Fujita, K.; Kato, Y.; Kitahara, Y. (1973). "Momilactones, Growth Inhibitors from Rice, Oryza Sativa L.". Tet. Lett. 14 (39): 3861–3864. doi:10.1016/S0040-4039(01)87058-1.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. ^ Toyomasu, T.; Kagahara, T.; Okada, K.; Koga, J.; Hasegawa, M.; Mitsuhashi, W.; Sassa, T.; Yamane, H. (2008). "Diterpene Phytoalexins are Biosynthesized in and Exuded from the Roots of Rice Seedlings". Biosci. Biotechnol. Biochem. 72 (2): 562–567. doi:10.1271/bbb.70677. PMID 18256463.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ^ Cartwright, D. W.; Langcake, P.; Pryce, R. J.; Leworthy, D. P.; Ride, J. P. (1981). "Isolation and Characterization of Two Phytoalexins from Rice as Momilactones A and B". Phytochemistry. 20 (3): 535–537. doi:10.1016/S0031-9422(00)84189-8.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ Kim, S.; Park, H.; Park, E.; Lee, S. (2007). "Cytotoxic and Antitumor Activity of Momilactone B from Rice Hulls". J. Agric. Food Chem. 55 (5): 1702–1706. doi:10.1021/jf062020b. PMID 17326606.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ a b Otomo, K.; Kenmoku, H.; Oikawa, H.; König, W. A.; Toshima, H.; Mitsuhashi, W.; Yamane, H.; Sassa, T.; Toyomasu, T. (2004). "Biological functions of ent- and syn-copalyl diphosphate synthases in rice: key enzymes for the branch point of gibberellin and phytoalexin biosynthesis". Plant J. 39 (6): 886–893. doi:10.1111/j.1365-313X.2004.02175.x. PMID 15341631.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ^ a b Sakamoto, T.; Miura, K.; Itoh, H.; Tatsumi, T.; Ueguchi-Tanaka, M.; Ishiyama, K.; Kobayashi, M.; Agrawal, G. K.; Takeda, S.; Abe, K.; Miyao, A.; Hirochika, H.; Kitano, H.; Ashikari, M.; Matsuoka, M. (2004). "An Overview of Gibberellin Metabolism Enzyme Genes and Their Related Mutants in Rice". Plant Phys. 134 (4): 1642–1653.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ^ a b Otomo, K.; Kanno, Y.; Motegi, A.; Kenmoku, H.; Yamane, H.; Mitsuhashi, W.; Oikawa, H.; Toshima, H.; Itoh, H.; Matsuoka, M.; Sassa, T.; Toyomasu, T. (2004). "Diterpene Cyclases Responsible for the Biosynthesis of Phytoalexins, Momilactones A, B, and Oryzalexins A-F in Rice". Biosci. Biotechnol. Biochem. 68 (9): 2001–2006. doi:10.1271/bbb.68.2001. PMID 15388982.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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