Crescenzi A M, Dodgson K S, White G F
Biochem J. 1984 Oct 15;223(2):487-94. doi: 10.1042/bj2230487.
A soil bacterium grown on propan-2-yl sulphate as sole source of carbon and sulphur yielded extracts containing an enzyme capable of liberating sulphate from racemic lactate-2-sulphate. The enzyme was purified to homogeneity by a combination of streptomycin sulphate precipitation of nucleic acids, batch treatment with DEAE-cellulose, and chromatography on columns of DEAE-cellulose, Sephacryl S-300 and butyl-agarose. The protein was monomeric with an Mr of 55 000-60 000. The enzyme activity was specific for D-lactate-2-sulphate (Km 6.6 nM; maximal specific activity 14.3 mumol/min per mg of protein) and showed no activity towards the L-isomer. The products of the enzyme's action were inorganic sulphate and D-lactate which were released in equimolar amounts and stoicheiometrically with the amount of ester hydrolysed. No L-lactate was formed. Retention of configuration implied cleavage of the O-S bond of the C-O-S ester link and this was confirmed by 18O-incorporation experiments in which 18O from 18O-enriched water in the incubation medium was incorporated exclusively and quantitatively into inorganic sulphate. Only two other esters (serine-O-sulphate and p-nitrophenyl sulphate) of a total of 29 compounds tested were substrates for the enzyme. D-Lactate, L-lactate-2-sulphate and the substrate analogues glycollate-2-sulphate and butyrate-2-sulphate were significantly inhibitory.
一种以硫酸丙-2-酯作为唯一碳源和硫源生长的土壤细菌，其提取物中含有一种能够从外消旋乳酸-2-硫酸盐中释放出硫酸盐的酶。通过硫酸链霉素沉淀核酸、DEAE-纤维素分批处理以及在DEAE-纤维素柱、Sephacryl S-300柱和丁基琼脂糖柱上进行层析的组合方法，将该酶纯化至同质。该蛋白质为单体，相对分子质量为55000 - 60000。该酶活性对D-乳酸-2-硫酸盐具有特异性（Km为6.6 nM；最大比活性为每毫克蛋白质14.3 μmol/分钟），对L-异构体无活性。该酶作用的产物是无机硫酸盐和D-乳酸，它们以等摩尔量释放，且与水解的酯量呈化学计量关系。未形成L-乳酸。构型保留意味着C-O-S酯键的O-S键断裂，这在18O掺入实验中得到证实，在该实验中，来自孵育培养基中富含18O的水的18O仅定量地掺入无机硫酸盐中。在总共测试的29种化合物中，只有另外两种酯（丝氨酸-O-硫酸盐和对硝基苯硫酸盐）是该酶的底物。D-乳酸、L-乳酸-2-硫酸盐以及底物类似物乙醇酸-2-硫酸盐和丁酸-2-硫酸盐具有显著抑制作用。
