A Brief Review of Nitric Oxide Synthase

一氧化氮合成酶之簡要回顧

王賢和(Shyan-Her Wang)

《童綜合醫學雜誌》 2卷2期 (2008/12) Pp. 63-68

https://doi.org/10.29838/TMJ.200812.0001

摘要

一氧化氮（NO）是細胞之間極為重要的訊息傳遞者。它參與了許多的生理與病理反應，例如，平滑肌的放鬆以及細菌或腫瘤的消除等。NO是由一氧化氮合成酶（NOS）所合成。NOS使用L-arginine和氧分子為基質，合成NO和L-citrulline。NOS可分為三種型態：ncNOS（type I），iNOS（type II）和ecNOS（type III）。ncNOS和ecNOS兩者為常態結構型，酶的活性和細胞內鈣離子濃度有關。相反地，iNOS為引發生成型，酶的活性和細胞內鈣離子濃度無關。NOS的抑制劑可分為L-arginine的相似胺基酸和guanidine分子的相似物兩大類。前者為L-arginine的競爭型抑制劑，通常對三種NOS之間比較不具選擇性或者對ncNOS和ecNOS比較有作用。相反地，後者對iNOS的選擇性作用較高。

並列摘要

Nitric oxide (NO) is a free radical and yet an important intercellular signaling messenger. It plays a role in many physiological and pathological processes including relaxation of smooth muscle, transduction of intercellular signals, killing of invading organisms and tumors, and damage of various cell components. NO is synthesized by the nitric oxide synthase (NOS). NOS uses L-arginine and molecular oxygen as substrates to synthesize NO and L-citrulline. There are three isoforms of NOS: neuronal constitutive NOS (ncNOS or type I NOS), inducible NOS (iNOS or type II NOS), and endothelial constitutive NOS (ecNOS or type III NOS). Both ncNOS and ecNOS are constitutive isoforms and are Ca^2+ and calmodulin-dependent enzymes. In contrast, iNOS is a Ca^2+-independent inducible isoforms in which the calmodulin molecule is tightly bound to the enzyme as a subunit of iNOS. Since L-arginine is the substrate to synthesize NO, most NO synthetic inhibitors are analogues for the amino acid, L-arginine, and are either nonselective or are more selective for constitutive NOS than iNOS. Alternatively, some NO synthetic inhibitors are not amino acids but are analogues for the guanidine group on L-arginine. Those inhibitors are more selective for iNOS than constitutive NOS.

並列關鍵字

nitric oxide ； nitric oxide synthase ； L-arginine ； guanidine ； constitutive ； inducible