Tramonti Angela, Contestabile Roberto, Florio Rita, Nardella Caterina, Barile Anna, Di Salvo Martino L
Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Piazzale Aldo Moro 5, 00185 Roma, Italy.
Istituto Pasteur Italia-Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche "A. Rossi Fanelli", Sapienza Università di Roma, P.le A. Moro, 5, 00185 Roma, Italy.
Life (Basel). 2021 May 14;11(5):438. doi: 10.3390/life11050438.
Cysteine sulfinic acid decarboxylase catalyzes the last step of taurine biosynthesis in mammals, and belongs to the fold type I superfamily of pyridoxal-5'-phosphate (PLP)-dependent enzymes. Taurine (2-aminoethanesulfonic acid) is the most abundant free amino acid in animal tissues; it is highly present in liver, kidney, muscle, and brain, and plays numerous biological and physiological roles. Despite the importance of taurine in human health, human cysteine sulfinic acid decarboxylase has been poorly characterized at the biochemical level, although its three-dimensional structure has been solved. In the present work, we have recombinantly expressed and purified human cysteine sulfinic acid decarboxylase, and applied a simple spectroscopic direct method based on circular dichroism to measure its enzymatic activity. This method gives a significant advantage in terms of simplicity and reduction of execution time with respect to previously used assays, and will facilitate future studies on the catalytic mechanism of the enzyme. We determined the kinetic constants using L-cysteine sulfinic acid as substrate, and also showed that human cysteine sulfinic acid decarboxylase is capable to catalyze the decarboxylation-besides its natural substrates L-cysteine sulfinic acid and L-cysteic acid-of L-aspartate and L-glutamate, although with much lower efficiency.
半胱氨酸亚磺酸脱羧酶催化哺乳动物中牛磺酸生物合成的最后一步，属于依赖磷酸吡哆醛（PLP）的I型折叠超家族酶。牛磺酸（2-氨基乙磺酸）是动物组织中含量最丰富的游离氨基酸；它在肝脏、肾脏、肌肉和大脑中大量存在，并发挥着众多生物学和生理学作用。尽管牛磺酸对人类健康很重要，但尽管其三维结构已得到解析，人类半胱氨酸亚磺酸脱羧酶在生化水平上的特征仍了解甚少。在本研究中，我们重组表达并纯化了人类半胱氨酸亚磺酸脱羧酶，并应用一种基于圆二色性的简单光谱直接方法来测量其酶活性。相对于先前使用的测定方法，该方法在简单性和减少执行时间方面具有显著优势，并将促进对该酶催化机制的未来研究。我们以L-半胱氨酸亚磺酸为底物测定了动力学常数，还表明人类半胱氨酸亚磺酸脱羧酶除了能催化其天然底物L-半胱氨酸亚磺酸和L-半胱氨酸外，还能催化L-天冬氨酸和L-谷氨酸的脱羧反应，尽管效率要低得多。
