Transcript 第五章 植物体内有机物的代谢

第五章
植物体内有机物的代谢
本章重点和难点：
一、植物体内有机物质的次级代谢；
 二、植物次级产物的合成途径。

第一节 各类有机物代谢的相互关系

蔗糖、淀粉等有机物来源于光合作用，通过呼吸作用分解产
生各种中间产物。

C3循环、EMP、TCA和PPP筑成了有机物代谢的主干。

糖和脂肪、蛋白质、核酸之间都可以相互转变。

丙酮酸、乙酰COA、α-酮戊二酸、草酰乙酸等中间产物起着
枢纽作用。
Plant Secondary
Metabolism
Plant metabolic pathways are linked
 These linkages include several key carbonbased primary metabolites(初级代谢物)
 As plants evolved, they found new
(secondary) ways to use metabolites
 Random mutations lead to a variety of
specialized plant secondary compounds

半纤维素
多糖
淀粉、纤维素
戊糖(Ru5P)→核苷酸→核酸
葡萄糖
脂肪
DHAP
PGAld
甘油 + 脂肪酸
C3途径
蛋白质
PEP
CO2
丙酮酸
酚类、萜类
化合物
乙酰COA
烟碱
AMP、
GMP
天冬氨酸族
酒精
谷氨酸族
乳酸
丙二酰COA
α-酮戊二酸
草酰乙酸
TCA
卟啉
(chl, Cyt)
第二节 植物体内的次级产物

次级产物：
是植物体内由糖类等有机物代谢衍生而来的物质。贮存
在液泡或细胞壁中，是代谢的中产物，不再参与代谢。

次级产物具有重要作用：
⑴是植物生命活动所必需的，如IAA、GA；
叶绿素和类葫萝卜素及花色素；木质素等，
⑵是植物组织色、香、味的主要构成成分，
⑶是药业或工业的重要原料。

植物的次级产物可分3类：
酚类、萜类、含氮次级化合物
一、 萜 类 terpene

萜类的种类：
萜类是以异戊二烯(isoprene)为单位组成的，
按其数目，可分为:
单萜(monoterpene)、倍半萜(sesquiterpene)、
双萜(diterpene)、
三萜(triterpene)、
四萜(tetraterpene)、 多萜(polyterpene)。
CH3
头
CH2 = C
CH = CH2
尾
Terpenoids: The largest group
Formed from 5-C subunits (isoprene) synthesized
from G-3-P, pyruvate, and acetyl-CoA
 Compounds have from 10 to >40 carbons
 Some terpenoids have functions in growth and
development

Plant hormones (gibberellins, abscisic acid)

Accessory pigments in photosynthesis
 Most terpenoids act as herbivory deterrents and
are a prime example of a “biochemical arms race”

Monoterpenes (C-10)
Pyrethroid insecticides拟除虫菊脂
 Conifer resins松脂
 Plant-plant defensive Communication防御沟
通
Deter pest
Attract pest predators
 Essential oils（Essential oils are often
stored in surface glands表面腺细胞）

Sesquiterpenes (C-15)
Herbivory deterrents威慑草食动物
(generalized)
 Bitterness
 Examples include
sagebrush山艾树 and
sunflower向日葵

Diterpenes (C-20)
Toxins and irritants毒与刺激 (generalized)
 Resins from some trees to seal herbivore
induced wounds松脂封闭取食伤口


Human use has adapted these compounds
to anti-cancer drugs (Taxol紫杉醇 from
Pacific yew紫杉)
Tri-terpenes (C-30)
More specialized toxins
 Steroid in structure结构类固醇
 Examples
Cardenolides – vertebrate heart toxins
脊椎动物心脏毒素
Saponins 皂角苷– detergent like
structure

一、 萜 类 terpene

植物体内重要的萜类物质：
挥发油：是单萜和倍半萜，樟树茎、柑橘果皮、薄
荷植株等
棉 酚：倍半萜，是重要的抗虫侵袭、抗真菌和细
菌的物质
固 醇：三萜的衍生物，质膜成分，植物蜕皮激素
的成分
类胡萝卜素：四萜衍生物，有叶黄素、胡萝卜素番
茄红素等，
橡 胶：多萜化合物
二、酚 类phenol

种类：按芳香族环上带有的碳原子数可分为
简单酚类、木质素、类黄酮类、鞣质类和其它
酚类

主要的酚类化合物有：
简单酚类：桂皮酸、咖啡酸、香豆素、水扬酸
木质素：没食子酸、木质素、
类黄酮类：花色素苷、黄酮、黄酮醇、异黄酮
鞣质类：缩合鞣质和可水解鞣质
Phenolic compounds
Common element is a phenolic group
 Derived from amino acids, principally
phenylalanine（苯丙氨酸）

Examples of phenolic compounds
and their roles
Phenylpropanoids（苯丙酸类化合物），具
有苯环-C3的基本骨架。
 Allelopathic compounds – inhibit plant
growth（A为咖啡酸、阿魏酸）

Examples of phenolic compounds
and their roles
Furanocoumarins 呋喃香豆素类(celery芹菜,
parsnip欧洲防风草, and parsley欧芹)
 Toxicity to insect herbivores（草食昆虫毒素）
 UV-activated toxins：UVA（320-400nm）激
发为高能电子态，插入DNA中，与胞嘧啶和
胸腺嘧啶结合，阻断DNA转录和修复，导致
细胞死亡。

Examples of phenolic compounds
and their roles
Benzoic acid derivatives（安息香酸派生物）
 Systemic resistance to pathogens（病原物
系统抗性）

Plant “immune systems”
Plant-wide response to a local infection
 May involve both toxic compounds like
oxygen radicals
 Can produce a memory response

Plant “immune systems”
Phytoalexins（植物抗毒素） are a primary
player in plant immune response
 Phytoalexins can be antimicrobial
terpenoids or phenolics （抗菌的萜或酚类）
 Synthesized in response to infection or
attack

Jasmonic acid – Stress and
defense hormone
Produced in response to a signal
transduction pathway
 Induces synthesis of other defensive
compounds
 Activates responses at the gene level

Examples of phenolic compounds
and their roles


Lignin木质素
Reinforcing molecule(esp. in woody tissue)组成
物质
Decreases palatability
Tannins丹宁
Flavor deterrent威慑味道，如涩味
Tea, blackberry,grape, apple
Mode of action is via protein binding蛋白鞣质结
合
Examples of phenolic compounds
and their roles
Flavonoids

Anthocyanins（花青素）: Pigmentation
(pollinator attractant)

Flavones and Flavonols（黄酮和黄酮
醇）: UV protection and bee
 Attractant（引诱剂）： (nectar guides花蜜
引导)

Isoflavones（异黄酮）: Antimicrobial
（抗菌）, antiestrogenic（抗雌激素）

三、含氮次级化合物




生物碱(alkaloid)：核酸的组分，亦是维生素B1、
叶酸和生物素的组 分， 它对动物有毒，可起防
御敌害作用；是重要药物的 有效成分，如奎宁、
吗啡、利血平、阿托品等。
含氰苷(cyanogenic glycoside)：豆类、禾谷类
和玫瑰中较多，本无毒，但释放HCN。
芥子油苷(mustard oil glycoside)：十字花科，
本无毒，但水解后产生有毒物质。
非蛋白氨基酸(nonprotein amino acid)：不构成
蛋白质的氨基酸，有毒性，有的阻止 蛋白氨基酸
的合成或吸收。
Nitrogen-Containing Compounds:
Only chemical similarity is the presence of
nitrogen somewhere in the molecule
 Well studied because of their toxicity to
animals and their medicinal value
 Perhaps the most easily-recognizable group
of secondary compounds in plants

Examples of N-containing
compounds and their roles

Alkaloids
A large group of compounds found in 20% of
all plant species

All contain a heterocyclic ring杂环 (i.e., a ring
formed from carbons and one nitrogen)

Best known for their pharmacological effect
on animals(动物药理学的效应)

Examples of alkaloids
Examples of N-containing
compounds and their roles




Cyanogenic glycosides含氰苷，存在与叶表皮的液
泡中
A large group of compounds found in
thousands of plant species
Stored in leaves (cherry樱桃, Johnson grass),
seeds (apple,peach), or roots (cassava木薯)
Enzymatic release of cyanide gas following
herbivory
Examples of N-containing
compounds and their roles





Glucosinolates (mustard oil glycosides)芥子油苷：
十字花科，本无毒，但水解后产生有毒物质。
Principally found in plants from the
Brassicaceae
Enzymatic release following herbivory
Volatile defensive compounds 挥发性防御物
(toxins, deterrents)
Can also serve as attractants引诱剂
Examples of N-containing
compounds and their roles
非蛋白氨基酸：不构成蛋白质的氨基酸，有
毒性，有的阻止 蛋白氨基酸的合成或吸收。
 Non-protein amino acids

Interfere with herbivore protein
synthesis

Replace normal amino acids to create
nonfunctional proteins
