Bojesen E
Scand J Clin Lab Invest Suppl. 1978;150:26-31.
A simple and rapid method is described for labelling serum lipoproteins with 3H cholesterol. According to the tracer data as well as cholesterol analyses, the velocity of ester formation in rat sera and beta-lipoprotein-depleted human sera decreased during incubations as a first order reaction. This suggests a level of chemical activity for cholesterol far below the Km of the enzyme. The reversible inhibition by three different penicillins showed a dependency of the inhibitor concentration which supports this notion. 50 per cent inhibition of the rat enzyme was obtained with 0.1 mM dicloxacillin, 0.3 mM benzylpenicillin, and 1.4 mM methicillin (water phase concentrations). The human enzyme was about 10-fold less sensitive. The mechanism of penicillin inhibition, investigated by stripping-recombination experiments with the 20-fold purified rat enzyme chromatographed on penicillin-loaded Sephadex G-25 columns, was found to be a dissociation of the enzyme into two components, an inactive apoenzyme and a coenzyme with a molecular weight below 1000.
本文描述了一种用³H胆固醇标记血清脂蛋白的简单快速方法。根据示踪数据以及胆固醇分析结果，在孵育过程中，大鼠血清和去除β-脂蛋白的人血清中酯形成的速度呈一级反应下降。这表明胆固醇的化学活性水平远低于该酶的米氏常数（Km）。三种不同青霉素的可逆抑制作用表现出对抑制剂浓度的依赖性，这支持了这一观点。在水相浓度为0.1 mM双氯西林、0.3 mM苄青霉素和1.4 mM甲氧西林的情况下，大鼠酶受到了50%的抑制。人酶的敏感性约低10倍。通过在负载青霉素的Sephadex G - 25柱上对纯化20倍的大鼠酶进行剥离 - 重组实验研究发现，青霉素抑制的机制是该酶解离为两个组分，一个无活性的脱辅基酶和一个分子量低于1000的辅酶。
