Markham G D, Tabor C W, Tabor H
J Biol Chem. 1982 Oct 25;257(20):12063-8.
A covalently linked pyruvoyl group is essential for the enzymatic activity of S-adenosylmethionine decarboxylase from Escherichia coli. A rapid purification method based on affinity chromatography is described for the isolation of this enzyme from an E. coli K12 strain which contains a plasmid containing the structural gene for S-adenosylmethionine decarboxylase, and which overproduces this enzyme. The purified enzyme contains one pyruvate moiety on each of six subunits. The enzyme is inactivated by incubation with carbonyl group reagents such as NaBH4 and phenylhydrazine; after inactivation, 1 mol of lactate or 1 mol of phenylhydrazone is found/mol of enzyme subunit. The enzyme is also inactivated by NaCNBH3 but only in the presence of either substrate or product and the divalent metal ion activator Mg2+; inactivation is accompanied by incorporation of 1 mol of the product, decarboxylated adenosylmethionine, per mol of enzyme subunit, suggesting that the pyruvoyl group participates in catalysis by formation of a Schiff base with the substrate. Equilibrium dialysis studies indicated a single substrate (or product) binding site/enzyme subunit.
共价连接的丙酮酰基团对于大肠杆菌S-腺苷甲硫氨酸脱羧酶的酶活性至关重要。本文描述了一种基于亲和色谱的快速纯化方法，用于从大肠杆菌K12菌株中分离该酶，该菌株含有一个携带S-腺苷甲硫氨酸脱羧酶结构基因的质粒，并且过量产生这种酶。纯化后的酶在六个亚基的每一个上都含有一个丙酮酸部分。该酶与羰基试剂如硼氢化钠和苯肼孵育后会失活；失活后，每摩尔酶亚基可检测到1摩尔乳酸或1摩尔苯腙。该酶也会被氰基硼氢化钠失活，但仅在底物或产物以及二价金属离子激活剂Mg2+存在的情况下；失活伴随着每摩尔酶亚基掺入1摩尔产物——脱羧腺苷甲硫氨酸，这表明丙酮酰基团通过与底物形成席夫碱参与催化作用。平衡透析研究表明每个酶亚基有一个底物（或产物）结合位点。
