• BMB Reports
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• 제36권2호
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• pp.149-153
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• 2003

The dibucaine number (DN) was determined for serum cholinesterase (EC 3.1.1.8, SChE) in plasma samples. The ones with a DN of 79-82 were used, because they had the "usual" SChE variant. The enzyme was assayed colorimetrically by the reaction of 5,5'-dithiobis-[2-nitrobenzoic acid] (DTNB) with the free sulfhydryl groups of thiocholine that were produced by the enzyme reaction with butrylthiocholine (BuTch) or acetylthiocholine (AcTch) substrates, and measured at 412 nm. Dibucaine, a quaternary ammonium compound, inhibited SChE to a minimum within 2 min in a reversible manner. The inhibition was very potent. It had an $IC_{50}$ of $5.3\;{\mu}M$ with BuTch or $3.8\;{\mu}M$ with AcTch. The inhibition was competitive with respect to BuTch with a $K_i$ of $1.3\;{\mu}M$ and a linear-mixed type (competitive/noncompetitive) with respect to AcTch with inhibition constants, $K_i$ and $K_I$ of 0.66 and $2.5\;{\mu}M$, respectively. Dibucaine possesses a butoxy side chain that is similar to the butryl group of BuTch and longer by an ethylene group from AcTch. This may account for the difference in inhibition behavior. It may also suggest the existence of an additional binding site, other than the anionic binding site, and of a hydrophobic nature.

• Applied Microscopy
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• 제18권2호
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• pp.34-46
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• 1988

췌장비 acinar cell에서 자극-분비 반응 과정을 알아보기 위하여 전자현미경을 이용하였다. 분비 촉진 물질인 아세틸콜린이나 MNNG의 투여에 따른 세포내 반응이 세포의 형태적 변화로서 잘 나타났으며 특히 guanylate cyclase를 활성화시키는 것으로 알려진 MNNG는 투여 후 일정시간 뒤 세포내에 많은 분비물 과립의 형성을 유발하였다. 이러한 결과에서 볼때 췌장의 acinar cell을 아세틸콜린으로 자극할 경우 guanylate cyclase는 지속적 반응 단계의 초기에 분비에 가세하는 것으로 생각되었고 cycloheximide나 dibucaine은 지속적 반응을 억제하는 것으로 나타났다. 또 췌장의 acinar cell에서는 분비물 과립의 형성이 소포체에서 직접 이루어지는 것으로 생각되었다.