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强啡肽的定义

强啡肽是一类内源性阿片肽，在大脑的许多不同部位产生，包括下丘脑、海马和脊髓，根据产生部位的不同，具有许多不同的生理作用。

Dynorphins are a class of endogenous opioid peptides produced in many different parts of the brain, including the hypothalamus, the hippocampus and the spinal cord, and have many different physiological actions, depending upon the site of production.

强啡肽的相关多肽

Dynorphins来源于前体蛋白proynorphin。当前强啡肽在加工过程中被前蛋白转化酶2（PC2）切割时，会释放出多种活性肽：强啡肽A、强啡肽B、“大强啡肽”和A/β-新强啡肽1。

Dynorphins arise from the precursor protein prodynorphin. When prodynorphin is cleaved during processing by proprotein convertase 2 (PC2), multiple active peptides are released: dynorphin A, dynorphin B, “big dynorphin” and a/ß-neo-endorphin【1】.

强啡肽的发现 

Dynophin于20世纪70年代中期在阿片受体和内源性阿片肽领域最重要的研究人员之一Avram Goldstein的实验室中被发现。Goldstein与日本生物化学家Shinro Tachibana合作进行了分子鉴定，以进行纯化，M.Hunkapiller和L.Hood进行了微测序。

Dynophin was discovered in the mid 1970's in the laboratory of Avram Goldstein, one of the most important researchers in the field of opioid receptors and endogenous opioid peptides. The molecular identification was achieved by Goldstein in collaboration with the Japanese biochemist, Shinro Tachibana for purification, and M. Hunkapiller and L. Hood, who performed the microsequencing.

强啡肽的结构特点

从猪垂体中分离出一种4000道尔顿的强啡肽（也称为“大强啡肽”）。它有32个氨基酸，氨基末端有一个称为强啡肽a的十七肽（17个氨基酸序列），羧基末端有一种相关的十三肽（13个氨基酸序列，强啡肽B）。这两种肽由“处理信号”Lys-Arg【2】分离。

A 4,000-dalton dynorphin (also called the “Big dynorphin”) was isolated from porcine pituitary. It has 32 amino acids, with a heptadecapeptide (17 amino acid sequence), called dynorphin A, at its amino terminus and a related tridecapeptide (13 amino acid sequence), dynorphin B, at its carboxyl terminus. The two peptides are separated by the "processing signal" Lys-Arg【2】.  

强啡肽的作用机制

Dynorphins主要通过一种名为？的G蛋白偶联受体发挥作用？-阿片受体（KOR）【3】。尽管KOR是所有强啡肽的主要受体，但这些肽确实对µ-阿片受体（MOR）、d-阿片受体、N-甲基-d-天冬氨酸（NMDA）型谷氨酸受体和缓激肽受体有一定的亲和力。不同的强啡肽在受体上表现出不同的受体选择性和效力。强啡肽和强啡肽A都比强啡肽B更有效、更具选择性。强啡肽通过与多巴胺神经末梢上的KOR结合来减少多巴胺的释放，从而导致药物耐受和戒断症状。

Dynorphins primarily exert their effects through a G-protein coupled receptor called the ?-opioid receptor (KOR)【3】 Although KOR is the primary receptor for all dynorphins, the peptides do have some affinity for the µ-opioid receptor (MOR), d-opioid receptor (DOR), N-methyl-D-aspartic acid (NMDA)-type glutamate receptor, and bradykinin receptor. Different dynorphins show different receptor selectivities and potencies at receptors. Both big dynorphin and dynorphin A are more potent and more selective than dynorphin B. Dynorphin decreases dopamine release by binding to KORs on dopamine nerve terminals, which leads to drug tolerance and withdrawal symptoms.

强啡肽的功能

Dynorphins调节疼痛反应。它们可以显著抑制吗啡或β-内啡肽诱导的镇痛作用【4】。Dynorphins抑制多巴胺的释放，这会抵消可卡因的愉悦作用【5】。它们通过控制食欲和昼夜节律来维持体内平衡【6】。除了在控制体重方面的作用外，还发现强啡肽可以调节体温【7】。

Dynorphins modulate pain response. They can significantly inhibit morphine- or beta-endorphin-induced analgesia【4】. Dynorphins inhibit dopamine release that would counter the pleasurable effects of cocaine【5】.  They are important in maintaining homeostasis through appetite control and circadian rhythms【6】. In addition to their role in weight control, dynorphins have also been found to regulate body temperature【7】.

References

1.     Day, R., Lazure, C., Basak, A., Boudreault, A., Limperis, P., Dong, W., et al. (1998). Prodynorphin processing by proprotein convertase 2. Cleavage at single basic residues and enhanced processing in the presence of carboxypeptidase activity. J Biol. Chem., 273(2), 829-836.

2.     W Fischli, A Goldstein, M W Hunkapiller, and L E Hood (1982). Isolation and amino acid sequence   analysis of a 4,000-dalton dynorphin from porcine pituitary. PNAS, 79 (17), 5435-5437.

3.     Nyberg, F. & Hallburg, M. (2007). Neuropeptides in hyperthermia. Progress in brain research,  162:277-93.

4.     FC Tulunay, MF Jen, JK Chang, HH Loh and NM Lee, (1981). Possible regulatory role of dynorphin on morphine- and beta-endorphin- induced analgesia. American Society for Pharmacology and Experimental Therapeutics, 219 (2), 296-298.

5.     Clavin, W. (2005). Dynorphin: Nature’s Own Antidote to Cocaine (and Pleasure?).

6.     Przewlocki, R., Lason, W., Konecka, A. M., Gramsch, C., Herz, A., & Reid, L. D. (1983). The opioid peptide dynorphin, circadian rhythms, and starvation. Science, 219(4580), 71-73.

7.     Xin, L., Geller, E. B., & Adler, M. W. (1997). Body temperature and analgesic effects of selective mu and kappa opioid receptor agonists microdialyzed into rat brain. Journal of Pharmacology and Experimental Therapeutics, 281(1), 499-507.

很多蛋白在细胞中非常容易被降解，或被标记，进而被选择性地破坏。但含有部分D型氨基酸的多肽则显示了很强的抵抗蛋白酶降解能力。