Haynes L W, Smith M E
Neuroscience. 1982 Apr;7(4):1007-13. doi: 10.1016/0306-4522(82)90057-4.
The effects of beta-endorphin (lipotropin 61-91) and related naturally-occurring peptides upon acetylcholinesterase activity in rat hind-limb muscles was investigated. beta-endorphin weakly inhibited the activity in a plasma membrane-enriched fraction. The inhibition by beta-endorphin of the membrane-associated acetylcholinesterase was less marked when the fractions were prepared from muscles which had been denervated 4-6 days previously. The membrane-associated acetylcholinesterase was solubilised from normal muscle preparations and separated by sucrose density gradient centrifugation into three major peaks (16S, 10S and 4S). beta-Endorphin inhibited the activity in the 16S peak but not that in the 10S and 4S peaks, whilst tensilon, a competitive inhibitor of acetylcholinesterase, inhibited the activity of all three peaks. beta-Endorphin inhibited the activity in the 16S peak but not that in the 10S and 4S peaks, whilst tensilon, a competitive inhibitor of acetylcholinesterase, inhibited the activity of all three peaks. beta-Endorphin inhibited the 16S activity in a concentration-dependent manner and its action was partly prevented if naloxone was added simultaneously. Purified natural porcine and bovine beta-endorphin were equipotent in terms of effective concentration range but the maximum inhibition was greater with the bovine peptide. beta-Lipotropin was approximately 4 times less potent than beta-endorphin, whilst C-fragment (lipotropin 61-87) was 100 times less potent. Prolonged treatment with collagenase did not reduce the catalytic activity of 16S acetylcholinesterase, but it was no longer susceptible to the inhibitory action of beta-endorphin. Kinetic studies indicated a complex type of inhibition by beta-endorphin (hyperbolic Lineweaver-Burke plot). Methionine enkephalin inhibited acetylcholinesterase in a weakly non-competitive manner and its action was not abolished if the enzyme was predigested with collagenase. beta-Endorphin produces a novel form of inhibition of acetylcholinesterase, acting only on the 16S (A12 or 'motor endplate-specific') form of the enzyme. The findings are discussed in the light of evidence that beta-endorphin-related immunoreactivity is expressed in motor nerve axons in the immature rat.
研究了β-内啡肽（促脂素61-91）及相关天然存在的肽对大鼠后肢肌肉中乙酰胆碱酯酶活性的影响。β-内啡肽对富含质膜的部分中的活性有微弱抑制作用。当从4-6天前已去神经的肌肉制备这些部分时，β-内啡肽对膜相关乙酰胆碱酯酶的抑制作用不那么明显。膜相关乙酰胆碱酯酶从正常肌肉制剂中溶解出来，并通过蔗糖密度梯度离心分离成三个主要峰（16S、10S和4S）。β-内啡肽抑制16S峰中的活性，但不抑制10S和4S峰中的活性，而乙酰胆碱酯酶的竞争性抑制剂腾喜龙则抑制所有三个峰的活性。β-内啡肽抑制16S峰中的活性，但不抑制10S和4S峰中的活性，而乙酰胆碱酯酶的竞争性抑制剂腾喜龙则抑制所有三个峰的活性。β-内啡肽以浓度依赖性方式抑制16S活性，如果同时加入纳洛酮，其作用会部分受到阻止。纯化的天然猪和牛β-内啡肽在有效浓度范围内效力相当，但牛肽的最大抑制作用更强。β-促脂素的效力约为β-内啡肽的四分之一，而C片段（促脂素61-87）的效力则低100倍。用胶原酶长时间处理不会降低16S乙酰胆碱酯酶的催化活性，但它不再对β-内啡肽的抑制作用敏感。动力学研究表明β-内啡肽的抑制作用较为复杂（双曲线型Lineweaver-Burke图）。甲硫氨酸脑啡肽以微弱的非竞争性方式抑制乙酰胆碱酯酶，并且如果酶先用胶原酶预消化，其作用不会被消除。β-内啡肽对乙酰胆碱酯酶产生一种新的抑制形式，仅作用于该酶的16S（A12或“运动终板特异性”）形式。根据β-内啡肽相关免疫反应性在未成熟大鼠运动神经轴突中表达的证据对这些发现进行了讨论。
