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首页> 外文期刊>Neurochemistry International: The International Journal for the Rapid Publication of Critical Reviews, Preliminary and Original Research Communications in Neurochemistry >The arylalkylamine-N-acetyltransferase (AANAT) acetylates dopamine in the digestive tract of goldfish: A role in intestinal motility
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The arylalkylamine-N-acetyltransferase (AANAT) acetylates dopamine in the digestive tract of goldfish: A role in intestinal motility

机译：金鱼消化道中的芳基烷基胺-N-乙酰基转移酶（AANAT）乙酰化多巴胺：在肠道运动中的作用

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摘要

Melatonin has been found in the digestive tract of many vertebrates. However, the enzymatic activity of the arylalkylamine-N-acetyltransferase (AANAT) and the hydroxindole-O-methyltransferase (HIOMT), the last two enzymes of melatonin biosynthesis, have been only measured in rat liver. Therefore, the first objective of the present study is to investigate the functionality of these enzymes in the liver and gut of goldfish, analyzing its possible daily changes and comparing its catalytic properties with those from the retina isoforms. The daily rhythms with nocturnal acrophases in retinal AANAT and HIOMT activities support their role in melatonin biosynthesis. In foregut AANAT activity also show a daily rhythm while in liver and hindgut significant but not rhythmic levels of AANAT activity are found. HIOMT activity is not detected in any of these peripheral tissues suggesting an alternative role for AANAT besides melatonin synthesis. The failure to detect functional HIOMT activity in both, liver and gut, led us to investigate other physiological substrates for the AANAT, as dopamine, searching alternative roles for this enzyme in the goldfish gut. Dopamine competes with tryptamine and inhibits retinal, intestinal and hepatic N-acetyltryptamine production, suggesting that the active isoform in gut is AANAT1. Besides, gut and liver produces N-acetyldopamine in presence of acetyl coenzyme-A and dopamine. This production is not abolished by the presence of folic acid (arylamine N-acetyltransferase inhibitor) in any studied tissue, but a total inhibition occurs in the presence of CoA-S-N-acetyltryptamine (AANAT inhibitor) in liver. Therefore, AANAT1 seems to be an important enzyme in the regulation of dopamine and N-acetyldopamine content in liver. Finally, for the first time in fish we found that dopamine, but not N-acetyldopamine, regulates the gut motility, underlying the broad physiological role of AANAT in the gut.
机译：在许多脊椎动物的消化道中都发现了褪黑激素。然而，仅在大鼠肝脏中测量了褪黑素生物合成的最后两种酶芳基烷基胺-N-乙酰基转移酶（AANAT）和羟吲哚-O-甲基转移酶（HIOMT）的酶活性。因此，本研究的第一个目标是研究这些酶在金鱼肝脏和肠道中的功能，分析其可能的每日变化，并将其催化特性与视网膜同工型进行比较。视网膜AANAT和HIOMT活性具有夜间夜相的日常节律支持了它们在褪黑素生物合成中的作用。在前肠中，AANAT活性也表现出日常节律，而在肝脏和后肠中，AANAT活性却没有规律性水平。在任何这些外周组织中均未检测到HIOMT活性，表明AANAT除了褪黑激素合成外还具有其他作用。无法检测到肝和肠的功能性HIOMT活性，导致我们研究了AANAT的其他生理底物，即多巴胺，在金鱼肠中寻找该酶的替代作用。多巴胺与色胺竞争，并抑制视网膜，肠和肝脏N-乙酰色胺的产生，表明肠道中的活性同工型为AANAT1。此外，在乙酰辅酶A和多巴胺的存在下，肠道和肝脏产生N-乙酰多巴胺。在任何研究的组织中，叶酸（芳基胺N-乙酰基转移酶抑制剂）的存在都不会消除这种产生，但是在肝脏中CoA-S-N-乙酰基色胺（AANAT抑制剂）的存在下，总的抑制作用会发生。因此，AANAT1似乎是调节肝脏中多巴胺和N-乙酰多巴胺含量的重要酶。最终，我们首次在鱼类中发现多巴胺而不是N-乙酰多巴胺能调节肠蠕动，这是AANAT在肠中广泛的生理作用的基础。

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