Williamson J M, Brown G M
J Biol Chem. 1979 Aug 25;254(16):8074-82.
L-Aspartate-alpha-decarboxylase, an enzyme that catalyzes the production of beta-alanine, has been purified to apparent homogeneity from Escherichia coli. The properties of the enzyme are: (a) pH optimum of 6.8 to 7.5, (b) temperature optimum of 55 degrees C, (c) Km for L-aspartate of 0.16 mM, and (d) molecular weight of 58,000. The activity of the enzyme is inhibited by reagents (hydroxylamine, phenylhydrazine, and sodium borohydride) that react with carbonyl groups, but no pyridoxal phosphate is present. The compound containing the carbonyl group has been identified as covalently bound pyruvate. Approximately 1 mol of pyruvate was found/mol of enzyme. That the enzyme has a biosynthetic function rather than a catabolic role is indicated by the observations that a mutant (designated as E. coli 99-2) which requires either beta-alanine or pantothenic acid for growth contains only trace amounts of enzyme activity, whereas it is present in substantial amounts in the parent strain (E. coli W) and in a spontaneous revertant of the mutant.
L-天冬氨酸-α-脱羧酶是一种催化β-丙氨酸生成的酶，已从大肠杆菌中纯化至表观均一。该酶的性质如下：（a）最适pH为6.8至7.5，（b）最适温度为55℃，（c）L-天冬氨酸的Km为0.16 mM，（d）分子量为58,000。该酶的活性受到与羰基反应的试剂（羟胺、苯肼和硼氢化钠）的抑制，但不存在磷酸吡哆醛。已鉴定出含有羰基的化合物为共价结合的丙酮酸。发现每摩尔酶约含1摩尔丙酮酸。观察结果表明该酶具有生物合成功能而非分解代谢作用，即需要β-丙氨酸或泛酸才能生长的突变体（命名为大肠杆菌99-2）仅含有痕量的酶活性，而在亲本菌株（大肠杆菌W）和该突变体的自发回复突变体中该酶大量存在。
