在丝足鲈（三星丝足鲈）盲肠中脂肪醇氧化为酸的过程

Oxidation of fatty alcohols to acids in the caecum of a gourami (Trichogaster cosby).

作者信息

Thyagarajan K, Sand D M, Brockman H L, Schlenk H

出版信息

Biochim Biophys Acta. 1979 Dec 18;575(3):318-26. doi: 10.1016/0005-2760(79)90100-0.

Abstract

Oxidation of fatty alcohols to acids in gourami caeca was investigated by measuring the reduction of NAD+ and the formation of labeled hexadecanoic acid from [1(-14)C]hexadecanol. Virtually all dehydrogenase activity is in the microsomal fraction. Maximal activity is obtained with NAD+ as cofactor whereas with NADP+ 60% of that activity is obtained. The enzyme is rather specific for long chain alcohols and 2 NADH are formed for each molecule of hexadecanol oxidized to acid. It is stabilized by mercaptoethanol, and completely inhibited by p-chloromercuribenzoate. The activity is optimal at pH 9.5. At higher pH, small amounts of aldehyde are found. The first reaction in the sequence, fatty alcohol leads to aldehyde leads to acid seems to occur under the more physiological condition at a much slower rate than the second reaction so that free aldehyde is not detected. Addition of palmitic acid indicated an uncompetitive product inhibition. The oxidation of alcohol to acid is reversible only to a very minor extent even in the presence of NADPH, CoA, ATP and Mg2+. Location, activity and properties of the enzyme are in agreement with the earlier observation from dietary experiments that in the gourami fatty alcohols of wax esters are oxidized to acids in the course of absorption.

摘要

通过测量NAD⁺的还原以及[1(-¹⁴)C]十六烷醇中标记的十六烷酸的形成，研究了丝足鲈盲囊中脂肪醇氧化为酸的过程。几乎所有的脱氢酶活性都存在于微粒体部分。以NAD⁺作为辅因子时可获得最大活性，而以NADP⁺时可获得该活性的60%。该酶对长链醇具有相当的特异性，每氧化一分子十六烷醇为酸会形成2分子NADH。它可被巯基乙醇稳定，被对氯汞苯甲酸完全抑制。其活性在pH 9.5时最佳。在更高的pH值下，会发现少量醛。该反应序列中的第一步，脂肪醇转化为醛再转化为酸，似乎在更接近生理的条件下以比第二步反应慢得多的速率发生，因此未检测到游离醛。添加棕榈酸显示出非竞争性产物抑制。即使存在NADPH、辅酶A、ATP和Mg²⁺，醇氧化为酸的反应也仅在非常小的程度上是可逆的。该酶的定位、活性和性质与早期饮食实验的观察结果一致，即在丝足鲈中，蜡酯中的脂肪醇在吸收过程中被氧化为酸。