Department of Chemistry, Texas A&M University, College Station, Texax 77840, United States.
J Am Chem Soc. 2011 Jan 19;133(2):379-86. doi: 10.1021/ja107424t. Epub 2010 Dec 16.
Thiocarboxylated proteins are important intermediates in a variety of biochemical sulfide transfer reactions. Here we identify a protein thiocarboxylate-dependent methionine biosynthetic pathway in Wolinella succinogenes. In this pathway, the carboxy terminal alanine of a novel sulfur transfer protein, HcyS-Ala, is removed in a reaction catalyzed by a metalloprotease, HcyD. HcyF, an ATP-utilizing enzyme, catalyzes the adenylation of HcyS. HcyS acyl-adenylate then undergoes nucleophilic substitution by bisulfide produced by Sir to give the HcyS thiocarboxylate. This adds to O-acetylhomoserine to give HcyS-homocysteine in a PLP-dependent reaction catalyzed by MetY. HcyD-mediated hydrolysis liberates homocysteine. A final methylation completes the biosynthesis. The biosynthetic gene cluster also encodes the enzymes involved in the conversion of sulfate to sulfide suggesting that sulfate is the sulfur source for protein thiocarboxylate formation in this system.
硫代羧酸化蛋白是各种生化硫化物转移反应中的重要中间体。在这里，我们在沃尔氏梭菌中鉴定出一种依赖蛋白硫代羧酸的蛋氨酸生物合成途径。在该途径中，新型硫转移蛋白 HcyS-Ala 的羧基末端丙氨酸在由金属蛋白酶 HcyD 催化的反应中被去除。HcyF 是一种利用 ATP 的酶，可催化 HcyS 的腺苷酸化。然后，HcyS 酰基-腺苷酸通过 Sir 产生的连二亚硫酸盐进行亲核取代，生成 HcyS 硫代羧酸酯。该反应在 PLP 依赖性反应中由 MetY 催化，将 HcyS 硫代羧酸酯添加到 O-乙酰高丝氨酸上，生成 HcyS-高半胱氨酸。HcyD 介导的水解释放高半胱氨酸。最后一步甲基化完成生物合成。生物合成基因簇还编码了将硫酸盐转化为硫化物的酶，这表明在该系统中，硫酸盐是蛋白硫代羧酸形成的硫源。
