Cunningham C, Tipton K F, Dixon H B
Department of Biochemistry, Trinity College, Dublin 2, Ireland.
Biochem J. 1998 Mar 1;330 ( Pt 2)(Pt 2):939-45. doi: 10.1042/bj3300939.
N-Chlorotaurine (taurine chloramine), formed by treating taurine with hypochlorous acid, was shown to decompose to sulphoacetaldehyde with a first-order rate constant of 9.9+/-0.5 x 10(-4).h-1 at 37 degrees C in 0.1 M phosphate buffer, pH 7.4. Rat liver homogenates accelerated this decay in a process that was proportional to tissue-protein concentration and saturable, with maximum velocity (Vmax) and Km values of 0.28+/-0.01 nmol/min per mg of protein and 37+/-9 microM respectively. This activity was found to be lost on heat denaturation, but retained after dialysis. There was no detectable formation of sulphoacetaldehyde when taurine itself was incubated with the tissue homogenates under the same conditions. Activation of human neutrophils (1.67 x 10(6) cells/ml) with latex beads resulted in a respiratory burst of oxygen-radical production, the products of which were partially sequestered by 12.5 mM taurine. Under these conditions sulphoacetaldehyde was generated at a constant rate of 637+/-18 pmol/h per ml for over 7 h. A non-activated neutrophil suspension contained constant levels of 1.42+/-0.02 nmol/ml sulphoacetaldehyde, as did activated cells incubated in the absence of taurine, a basal level which may indicate a steady turnover of taurine in these cells. Such formation of chlorotaurine and its decay to the aldehyde may be the first steps in the metabolism of taurine to isethionate (2-hydroxyethanesulphonate) that has been demonstrated by various authors to occur in vivo.
用次氯酸处理牛磺酸形成的N-氯代牛磺酸（牛磺酸氯胺），在37℃、pH 7.4的0.1 M磷酸盐缓冲液中，以9.9±0.5×10⁻⁴ h⁻¹的一级速率常数分解为磺基乙醛。大鼠肝脏匀浆加速了这种分解过程，该过程与组织蛋白浓度成正比且具有饱和性，最大速度（Vmax）和Km值分别为每毫克蛋白0.28±0.01 nmol/min和37±9 μM。发现这种活性在热变性后丧失，但透析后仍保留。在相同条件下，将牛磺酸本身与组织匀浆一起孵育时，未检测到磺基乙醛的形成。用乳胶珠激活人中性粒细胞（1.67×10⁶个细胞/ml）会导致氧自由基产生的呼吸爆发，其产物部分被12.5 mM牛磺酸螯合。在这些条件下，磺基乙醛以637±18 pmol/h每毫升的恒定速率产生超过7小时。未激活的中性粒细胞悬液中磺基乙醛的含量恒定为1.42±0.02 nmol/ml，在无牛磺酸的情况下孵育的激活细胞也是如此，这个基础水平可能表明这些细胞中牛磺酸有稳定的周转。氯代牛磺酸的这种形成及其向醛的分解可能是牛磺酸代谢为羟乙磺酸盐（2-羟基乙烷磺酸盐）的第一步，多位作者已证明这种代谢在体内会发生。
